Question: With all the focus on image blocking by ISPs, is there any way to use animation in emails? I keep hearing it’s supposed to give me a better click through rate and ROI, but is it even something I should consider?

Answer: Depending on your audience and your email goals, you might be able to use animation in email campaigns, but only as a small animated GIF. Do not use Flash or movie files, because your subscribers’ email clients might not be able to render them, and because ISPs are more likely to block emails that incorporate these applications.
Yes, the images might be disabled. Depending on the email client, your subscriber might see only the first frame of your animated GIF. This is true for Outlook 2007, for example. But if your readers are turning on your images or clicking through on your view-online link, then the animated gifs will be displayed, and you can create the effects you desire.

Before you launch a whole campaign using animation in the email message, be sure to test it thoroughly for functionality and audience acceptance. To test function, view the message on different platforms, including desktops, laptops and handhelds – and in different email clients and browsers.

Also run a message with animation on a sample of your audience and see if you notice a difference in response. You might even survey them briefly afterward to get qualitative data on their reactions.

Question: We took a lot of time to create an email message template that uses a lot of color and images because we read that HTML converts better than plain text. But all that work is wasted because the big ISPs like Yahoo! and Hotmail block everything but static images. Why are they doing this and what do I have to do to get them to show my images?

Answer: This is an issue that marketers are just going to have to accept and try to work with for now. The ISP’s main goal is to protect their customers, not to deliver your email, even if their customers requested it. They see images as doorways to many security problems, such as and opening a door to malicious downloads and increased spam.

ISPs that disable images by default – meaning users have to change a setting to allow images to download automatically – have seen security problems decrease, prompting other ISPs to follow suit. Don’t expect to see a change in this for the time being, at least not until authentication is adopted by all senders and considered a secure method of identifying legitimate email.

However, you can work around default image-blocking with these three strategies:

1. Go directly to readers and tell them how they can activate downloading
2. Cooperate with ISPs that offer automatic downloading to reputable senders
3. Redesign your templates to show important content to your readers despite image-blocking.
These strategies will help you stand out from other marketers who don’t make the effort. Do nothing, and your email program will struggle with poor performance.

Question: I want to juice up our transactional emails so we can get some marketing mileage out of them, because they have a better open rate than our regular newsletters. What can I do that will keep them legal?

Answer: Transactional emails represent an untapped resource because recipients look for them and open them more often. You have some latitude to add some marketing content to emails sent to confirm a purchase, registration, bill payment or other transaction. But remember, the primary purpose of the email must be to provide the transactional information.

If half or more of the content is commercial, though, it tilts the balance from transactional to commercial. In particular, you would need to add a working unsubscribe link and physical postal address, which is never a bad practice for any message, transactional or not.
Three tips:

• Add only 1 commercial element such as an opt-in invitation, a link to related or complementary purchases, or an offer to download a white paper.
• Place the commercial material in the bottom half of the message body so that the transactional element is clearly visible at the top of the email, in case the recipient reads the message in the preview pane.
• Make sure the subject line reflects the transaction, not the offers.

Question: I have heard that Outlook 2007 will make HTML messages unreadable. Since I am a business marketer, and I presume most of my readers use Outlook to read business email, does this mean I have to give it up completely and send out only text email from now on?

Answer: In a word, no. You do not have to abandon your HTML format, which gives you several advantages over text in terms of reporting, tracking, branding and pull with readers. However, you should review how you use HTML and create a “light” version if you don’t already have a text-only edition.

Essentially, Outlook 2007 will not be able to read many HTML functions as effectively anymore, now that Microsoft has replaced Internet Explorer as the HTML rendering device with MS Word, which interprets and renders HTML code less effectively.

Consider trading out high-function features such as in-message forms and rich media to create a leaner, more streamlined format using text to report information, describe products or issue calls to action.

You don’t have to revamp all of your email templates to reflect this lighter version, unless you know your audience relies more heavily on Outlook 2007 than other email clients. Instead, create this special version specifically for subscribers who use Outlook 2007, and promote it both in your HTML edition and on your subscription and preference pages.

Question: I know I should be asking for my customers' email addresses when they are either in my shop or at my Web site but should I ask for it before, during or after the sale? I don't want to scare them away from buying if they don't really want to hand it over.

Answer: A rule of thumb for both online and in-world: Never wait until you have closed the till before asking your customers if they would like to sign up for your newsletter or email offers.

In a physical shop, ask for the address just as you are about to complete the sale, just after you have totalled the purchase and while you are either counting change or processing the credit card. Take advantage of those few seconds of dead air present in every sales transaction to explain briefly why the customer should sign up for your program. If you wait until after you finish the sale, you will most likely lose the opportunity to obtain an email address since the customer has no compelling reason to stay once the sales transaction is finished.

For online purchases, you should have a subscription blank or link to your preference or registration page on every page of your site, and certainly on the transaction page, confirmation page, confirmation email and any follow-up emails you send. Be sure to draw the customer's attention by stating subscriber benefits – "Sign up to receive email-only offers and product news" – instead of a dull "click here for our newsletter" slogan.

Question: How can I provide a readable message for subscribers who read email on their mobile phones or PDAs? There isn't any technology that makes HTML render properly on mobile devices.

Answer: You are right to be concerned about having your messages render legibly on ever-shrinking screens. Walk through the nearest sopping centre or airport, and look at all the people squinting at their mobile phones or PDAs. Many mobile platforms don't properly render HTML either. You can see that the future of email depends ever more on readability.

This problem has an easy answer though: Create a text-only version of your HTML newsletter and offer a link to the text version just as you would a Web version, at or near the top of your email.

If you suspect you have a large number of mobile readers, this is something you could do to improve readability for your newsletter, stand-alone ad or other email messages you typically send in HTML, in order to meet the needs of as many subscribers as possible.
Promote the text version as a benefit for your mobile readers on your sign-up form. Also, keep the link to your Web or text version short and self-explanatory so that as much of it shows up on a tiny mobile screen as possible.

Examples:
Too long: "To see the Web version of this newsletter, please click this link."
Better: "Mobile Version, Web version online."

Question: Is it ever okay to send email content as a file attachment in a PDF? I get tired of having spam filters block my newsletter as spam. Plus, I send out special reports to new subscribers, and those are too long to put into a regular message.

Answer: Don't do it! Attaching any file to a bulk email message is much more likely to get your message blocked at more ISPs because it is a potential virus threat.

To protect your newsletter from spam filters, you'd be better off in the long run reviewing both the content and the text and HTML templates to make sure nothing in it unduly triggers a filter. Besides, you don't want to put an extra barrier between your content and your readers. Those who scan email in a preview pane or on a mobile phone might neither see nor be able to open the link to get to the PDF, and others never download attachments.

On the other hand, when you need to distribute special reports, white papers, premium content or rich media that would consume a lot of bandwidth to download via email, you should house that material at your Web site. This protects it from anti-spam programs that could filter it for potential content or virus threats and also gives you another chance to sell your readers or visitors on the benefits of the information they requested.

If the content is an incentive for subscribing to your email program, just drop the link into the email confirmation and promote it with enticing copy that will send the reader racing to your site to download it.

Answer: Yes, they do, and they're more important than ever, now that major desktop email clients such as Outlook and Web clients like Yahoo! Mail block images unless recipients specifically request to view them.

The ALT tag is an HTML code that describes its accompanying image. It's what you see instead of an image if you block images in email. Here's why you need to optimise your use of ALT tags in email messages:

1. Not having ALT tags associated with images is a spam signature. It can raise your spam score, trigger a filter and contribute to your email being blocked or routed to the junk folder.
2. ALT tags give recipients who block images more reason either to click on the image or to show the image in their email client. They're especially important if you don't use a lot of text in your creative content.

This means you have to spend almost as much time creating a useful and descriptive ALT tag as you do on the rest of the email copy. A tag that says merely "click here" doesn't give the reader any incentive.

A good ALT tag has two to 10 short words that either describe the image or specify the action you want the recipient to take. Use them on every image that helps your reader know instantly who you are and why they should pay attention to you, such as your logo and action items including unsubscribe, forward to friends and contact information.

Here are some real-world examples: "SmarterTravel.com Deal Alert," "Save 75% on winter coats;" "Click for 50% off peak rates," "Forward this newsletter to friends."

Question: If FREE is such a bad word to use in an email subject line or in the message, why do I get so many emails in my own inbox that say "free shipping?" Shouldn't they all go to my junk folder?
Answer: It usually takes more than a moderate use of the word "free" in a message subject line or content to trigger a spam filter or block. A few years ago, however, when content scoring was less sophisticated, many ISPs and corporate email servers blocked unwanted email that contained even one word associated with spam like "free." So, any email message, even personal email or messages coming from trusted sources, was filtered to the junk folder or banned outright.

Today, content-scoring programs such as SpamAssassin look at multiple factors that make up a possible spam or fraudulent message and assign points each time a factor matches one of its filters. If the total point value exceeds the ISP or email server's allowed limit, the message will get blocked or filtered as spam. One use of "free" usually isn't enough to trigger a block or filter. However, if you have enough other problems, such as broken HTML coding, and if you use the word many times or in all capital letters, the fraction of a point you get penalised could put you over the limit.

Question: We use the same subject line for each issue of our bi-monthly newsletter. Do you have any statistics to show whether this is an advantage or a disadvantage for our "read" percentage?

Answer: There aren't any reliable statistics that show whether a subject line that never varies will draw better or worse than one which changes to reflect the new content in each issue. You can test this on your own audience, however, using a standard A/B split test.

Divide your database in two. Email the newsletter with the standard subject line to one segment, then create a unique subject line for the other segment. Do this for at least three publishing cycles, and always send the same subject-line configuration to the same segment of your database. Then, compare the results. If you see a difference of more than 5 to 10 percentage points in your open statistics, it's probably significant enough to drive your decision.

When you repeat the subject line over and over, you don't give readers a compelling reason to open the email. We believe the best practice is to create a unique and compelling subject line for each issue.

You can create a subject line that's both instantly familiar AND unique each time by incorporating your newsletter name in either the sender line (the "from" line) or by putting it first in the subject line. We do this by setting it off in brackets first in the subject line and then summing up the key content in two to three words (any more than that and the inbox view could cut it off).

Question: Besides personalising with the recipient's name, what else can we do to make our emails stand out in the inbox? We are worried about getting lost in all the discounts and free shipping messages from other companies.

Answer: This is a concern all year long for email marketers, but it becomes more crucial as the holiday shopping season heats up and creates even more clutter in your recipient's inboxes.
These three strategies will make your email more eye-catching in the inbox:

1. You might be thinking about subject lines, but first make sure your sender ("from") line lists your company, brand or newsletter name. That will catch your reader's eye.
Our research shows the sender line is the No. 1 factor that readers use to decide whether to open or delete an email. An email address instead of a name, or a department or employee's name doesn't deliver the same information.
Regarding the subject line: If you can't put your company or brand name in the sender line, list it first in the subject line.
2. Announce the offer right in the subject line. Don't be coy and hint at what's inside ("Save 10% this week only" instead of "Open to find your special savings").
3. Make sure the offer's key elements appear in the first 50 or 60 characters. That's all many email clients will show in the inbox. Don't wait until the end to deliver the hook.

Question: We have been getting complaints lately from subscribers that they are having a hard time reading our emails (links are broken, 'submit' buttons don't work). You have said before that we should test our messages before they go out, but when we do that, they look fine. What are we doing wrong?

Answer: You probably aren't testing it to enough email clients. It looks good when you read it in Outlook on your PC, but your subscribers who read in Outlook Express on their iMacs are probably the ones complaining that the submit button doesn't work.

It's easy to fix, though. You can either sign up with a third-party verification service that reviews your messages across a broad swath of clients and platforms, or you can do it yourself by creating accounts at some of the major email providers.

Telfis offers a rendering service that can highlight trouble spots across a host of email clients.

How to DIY

You probably won't be able to cover as many bases on your own but you can hit the ones that are most important to your readers.

1. Identify your target email clients or services.

If you send to the business or technical communities, your readers likely are using a business-class client such as Outlook or Lotus Notes on PC desktops or laptops, or even a handheld like a BlackBerry or Treo. However, graphics or media-orientated readers are more likely to use Macs, which uses a different OS from Windows, which powers most PCs.

Consumers most likely read email in a Web-based client (Hotmail, Yahoo, Gmail or Earthlink), a standalone pay service such as AOL or a desktop email client provided by their ISP (e.g. Outlook Express). Younger subscribers might read you on their mobile phones, which are even more limited in reading capacity than their parents' BlackBerries.

2. Send each message (excluding one-to-one emails such as transactionals or customer follow-ups) to your test accounts before you send to your full mailing. Review it on different platforms if you can (PC, Mac, laptop, handheld). Click all links and buttons, and be sure every other element renders as intended.

Rendering problems that crop up most often are clickable buttons or graphics that don't work, formats that shrink or stretch on the screen or have entire copy or graphics blocks shoved out of place, and default typefaces that can play havoc with any specialised typography.

3. Add your test account addresses to your regular mailing lists to monitor delivery issues such as blocking or filtering to junk folders.

Final Word

This is another argument for creating HTML messages that are as lightweight as possible, avoiding the use of frames, scripts, streaming sound and video or any other tricks that suck up bandwidth. A streamlined and attractive HTML message that renders properly for everybody will do more than one that's tricked-out but unworkable.

Answer: The click-through rate is important because without it, you don't get conversions. However, there's no single benchmark click-through rate, because CTRs depend on many factors: whether you send to a business or consumer audience, the kind of mailing you send, how relevant it is to your audience, how often you send, your opt-in process, your use of personalisation and segmentation and dozens of other factors. Most significantly, how many links you have in your email and if you are providing content such as articles, whether you include the entire article within the body of the email or you have a teaser or snippet that requires subscribers to click through to a Web site to read.

Beyond that, many companies calculate and report CTRs differently - using total rather unique clicks. Many subscribers will click on multiple links, which means that CTRs based on "total" clicks are typically about two times higher than those based on "unique" clicks..
That being said, below are some ranges for average CTRs for permission-based house lists. CTRs that we cite are based on unique clicks (only one click per person is counted) and are calculated as: unique clicks/emails delivered:

• B2B newsletters typically range from 5% to 15%. If yours are consistently below that level then among other things, you are probably providing content of little value to your subscribers. Or you may have most of the content within your email, not giving subscribers a reason or means to click-through to your site.
• B2C promotional emails often range from about 2% to 12%. Emails with less than a 2% CTR may be a result of over mailing and questionable opt-in processes.
• Highly segmented and personalised lists (B2B and B2C) are often in the 10% to 20% CTR range. Also, email messages with very strong content but sent to unsegmented lists, like many news or trend-type newsletters, are often in the 10%-15% range.
• Trigger or behavior-based emails (emails that are sent to a recipient based on some behavior they showed, such as clicking on a product link, visiting a specific Web page, etc.) are often in the 15% to 50% range.
If your emails are typically showing under say 2-3% CTRs, some of the causes likely include:
• Poor permission or opt-in processes. This includes pre-checked boxes, not making it clear what type of email they will be receiving, automatically adding someone to receive your email when they've actually signed up for something else such as a whitepaper, etc.
• Poorly written subject lines that do not direct and motivate recipients to take an action.
• Poor delivery rates. If a lot of your emails are getting blocked or filtered and you don't know it, your CTR will obviously be affected.
• Poor open rates. If few people open your email, fewer recipients have a chance to click.
• Poor design and layout. If they can't easily find where to click through or aren't motivated to by your layout.
• Lack of links. Quite simply, the more links the better. Make it so that readers are continuously stumbling over text and graphic links like they do signage in a retail store.
• No reason to click. If your newsletter has a single or multiple articles in their entirety, then don't expect them to click. You haven't given them any reason. If you are sending a promotional email and you don't include a deadline for the offer, or convey a discount, special offer, limited supply, etc., few people are probably going to take action.

Answer: There are dozens of variables that go into open rates - making the "average" question so difficult. That being said, we believe that open rates (measured using unique opens - meaning only one open per recipient is counted) for most newsletters should be in the 30 to 45 percent range, with most companies that are doing a good job probably falling into the 35-40% range. Companies using the double opt-in process, with mostly newer subscribers, offering extremely compelling content and following best practices can achieve open rates in the 45 to 50+ percent range.

Open rates have been declining a bit for a couple of reasons. Blocked images and preview panes mean that some emails are "viewed" but not counted as "opens." Additionally, as people's inboxes have gotten overwhelmed combined with them subscribing to more and more newsletters, people are making choices about which newsletters are of value and are then opening fewer - even though they may not unsubscribe.

Answer: Today, the vast majority of all email clients can render HTML emails fairly well (notable exceptions being older versions of Lotus Notes and pre AOL 6.0). So whereas a few years ago the answer to the question was rather complex, today it really comes down to message purpose, subscriber preference and multipart messaging. In our experience roughly 95 percent of commercial messages sent today are sent as HTML/Multipart.

• Message Purpose – However, certain types of messages can lend themselves to plain text format, including – alerts, correction/mistakes, confirmations, breaking news, etc.
• Subscriber Preferences – Most newsletter subscribers today prefer the attractive nature and usability of HTML emails. But some percentage of subscribers still prefer plain text, and in certain vertical markets like software programmers, some newsletter publishers have seen as much as 95 percent of their subscribers preferring plain text. Regardless, the key is to offer subscribers the choice of format when they opt-in to your newsletter.
• Multipart Messaging – Most email technology solutions send HTML messages as “multipart” messages. This means that the message is sent in “multi-parts” – in this case both HTML and plain text. When a subscriber’s email client receives a multipart message, it accepts the HTML version if it can render HTML, otherwise it presents the plain text version. Additionally, some recently upgraded clients, such as Outlook 2003, enable users to choose to accept HTML or plain text messages by default.

Answer: A separate reply-to address for each newsletter allows you to track replies and manage responses better. It's not a requirement; however, a single address could be a problem if one newsletter generates more spam complaints and bounces than the others.
Assuming you send all three newsletters from the same IP address, and each newsletter has its own mailing list, the "bad" list could trigger ISP filters that would either block all your newsletters or send them to recipients' bulk folders. Examine your delivery reports, and review the messages in the reply mailbox for red flags.
If you do go with a single reply address, remember these key elements:

• Label the address with the purpose ("reply@") and your company, brand or newsletter name. Example: reply@MyCompany.com.
• Use an email account that multiple users can access instead of a personal account. You don't want to deal with all the automated replies, such as out-of-office notices, that will flood in right after you hit "send."
• The reply address isn't the same as the "from" or sender address. The "from" address should be as specific as possible, because many recipients use it to identify the sender or decide whether or not to open the email. Example: Newsletter@MyCompany.com.
• Monitor the reply mailbox during and after each delivery as well as between deliveries. Watch for spam complaints, challenge-response replies and personal comments, questions or unsubscribes, and deal with these personally and immediately.

Answer: In general content/HTML code and black lists are the most likely to trap your emails. Generally only organisations with very large lists – sending several hundred thousands of emails to a single ISP – are likely to have their emails filtered based on volume. For our large volume clients, Telfis limits the volume of emails sent per hour to certain ISPs. If you conduct ongoing list hygiene, including removing hard bounces, unsubscribes, people filing spam complaints and minimise email addresses with bad syntax upon opting in, your bounce percentage should fall well below the danger zone with ISPs.

Answer: The fact that you are a "respected organisation" is irrelevant to ISPs and corporations. Their spam filters and algorithms are looking at whether email coming from your IP address is trusted and is not on black lists; and at the code and content of the individual email. Subject lines are only one component of what the filters look at from a content perspective.

As mentioned above, code and content filters generally assign positive and negative points to messages based on what is perceived to be good practice and bad or the practices of spammers. The subject line you mentioned – "enter online contest and win prizes!" – is not likely to cause your message to be filtered by itself. But the subject line is rather aggressive and is likely to increase the number of points for a message. Specifically, we recommend not using exclamation points in emails when they can be avoided. By itself, an exclamation point generally isn't problematic, but in combination with words such as "free" your email may be filtered by the Outlook default filter.

Further, "enter online contest and win prizes" reads very much like a spam email. It is neither specific, nor does it appear to be something one would expect from a "respected and credible organisation." The challenge of course is to find the right balance of aggressive and exciting copy that motivates subscribers to open their emails, but at the same time does not trigger, or contribute to, being filtered. In your example, try some different subject lines testing for the best combination of delivery and your key metrics – number of contest entries, purchases, new memberships, etc. An example might include:

• {Organisation name here} Register to Win Special Edition Posters
Whether you use a content checker or not, set up proof lists and send your messages to key domains such as Yahoo, AOL and Hotmail before emailing to your entire list.

Answer: Well, the right buzz words to use in subject lines are probably going to vary greatly by the purpose and value of your email newsletter. In the ecommerce world, words and phrases such as "free shipping," XX% Off; "Sale Ends Friday" and others have proven to perform well. For newsletter publishers distributing news-based emails, buzz words are probably less important than simply writing compelling subject lines that convey that day's or week's hottest and most interesting news story – as perceived by your subscribers. For corporate, trend and less time-sensitive newsletters, practical words and phrases such as XX Tips, X Steps, X Ways, etc. seem to pull well. Like every answer in email marketing, you need to test various approaches and determine which ones work best for you and your subscribers.

Answer: As noted above, all quality email marketing solutions track open rates for you. The industry standard way of tracking “opens” is by including a small clear image (hosted on a server). When a user opens the email, or views the email in the preview pane (if images are enabled), the image loads from the server and signifies the email has been opened. Using embedded images in HTML emails is not a common practice for professional emails. By embedding images within the email you lose control over how the image will appear. In many email clients the image may appear distorted, be in the wrong position or the wrong size. Hosting images on a Web server generally ensures that images appear as you've intended.

Answer: All quality email marketing technology solutions on the market today – whether ASP (Web hosted) or installed software – enable users to manage their lists and opt-in process, personalise and segment their emails, manage bounces and unsubscribes, track opens, clicks, bounces, unsubscribes, spam complaints, etc – and much more. We of course believe Telfis offers the best combination of advanced features, support and price/value – but regardless, when selecting a vendor or solution you need to keep various criteria in mind, including:

• Your budget – how much you've allocated toward email marketing will drive which types of vendors you can and should consider.
• Is email marketing strategic to your business/organisation?
• Do you have advanced technology needs such as triggers, API integration, detailed reporting, potentially custom features, etc.?
• How important is deliverability to your organisation?
• How important is training and support?
• Do you have a need for services – such as HTML template design, performance improvement consulting and program audits?

Answer: Most public black lists will have their de-listing criteria and process described on their Web site. Typically it's simply a matter of contacting the administrators of the list and complying with their requirements. The easiest way to stay off black lists is to never appear on them in the first place. Through following email subscription best practices, such as confirmed opt-in methods and continuous bounce and complaints management, your risk of being black listed is greatly lessened.

Answer: Each of the ISPs utilise their own filtering algorithms, software block lists and processes – so it is not uncommon to have very different results across ISPs.

As outlined in some of the articles referenced below, the first step is to actually identify if you are having one time, sporadic or on-going issues at specific ISPs and domains. If you have on-going performance of filtering problems it may be that your IP address or that of your email service provider is on either an internal ISP black list or a third-party black list being used by the ISP. Alternatively, it is likely that your messages contain improper HTML coding or consistently used content that the ISP is filtering.

As mentioned above, some ISPs have white lists, so it is important to be a “good emailer,” follow best practices and get your IP address white listed.

But in general it is not a matter of “getting past” these filters, but rather determining what’s causing your messages to be filtered and then correcting the problem.

Answer: Below are a couple of strategies to determine the optimal time to send an enewsletter:

• Survey your subscribers via email as to what time of the day they would most like to receive emails – and give them a half dozen time periods to choose from. Then send emails to the responding subscribers based on their preferences.
• Assuming you have an opt-in form on your Web site, allow the subscribers to select the time period they'd like to receive emails when then subscribe.
• Conduct a mini focus group by contacting a dozen of your subscribers and finding out what time they'd like to receive emails. Use these conversations to also learn what types of information and format would be most valuable and preferred.
• Test. The best method is always to conduct split tests. Segment your list into equal random groups and email the identical message to each segment at key time periods (keeping in mind differences by time zone).
• Consider segmenting based on time zone. Since it sounds like you have their mailing addresses, segment your list according to their state/zip code and corresponding time zones. When you've determined optimum mailing times this ensures that your message reaches subscribers across the country all at the same local time period.

Answer: Telfis has analysed unsubscribe rates across our entire client base revealing an average rate of 0.17 percent per month. While there is no hard and fast rule, an unsubscribe rate above 0.50 percent would likely suggest some significant problems with your email program.

Answer: Most email list-management programs remove undeliverable addresses after they bounce two or three times. But, because the addresses are not being reported to you as bounces, your removal function doesn't act. Thus, the old addresses hang around on your list and drag down your metrics.

So, you'll have to remove those addresses manually. First, audit all the domain names on your mailing list to find those that are out of date or obsolete, like those you mentioned. Your software should allow you to order your addresses by domain name (the part that comes after the @ symbol). Once you order your list by domain, find the obsolete domains and delete all the email addresses associated with them from your list.

You probably have many other dormant addresses lurking in your list, too, either because some recipients delete your emails without opening or move on to new addresses without unsubscribing. Pre-Gmail, when Web clients such as Hotmail and Yahoo! gave users a comparatively stingy 2MB of storage space, those addresses would bounce sooner because the mailboxes filled up faster. Today, 1GB and 2GB mailboxes take longer to overflow. That means addresses hang around longer without bouncing.

The problem is, you don't know which addresses belong to out-of-date or obsolete domains and which belong to people who don't bother to open or don't live there anymore. So, give them a chance to reconnect with you by implementing a “reactivation program”. And if they don't, boot them off your list.

Create a sublist of any email address that has generated no action, open or click, for a set period, say one year. Send a message inviting those users either to resubscribe or unsubscribe. Give them a week or so to respond, and then scrub any nonresponding addresses from your master list.