Email Marketing

21 Ways to Improve Email Deliverability

Editor’s Note: This article was originally published by Web Marketing Today. Practical Ecommerce acquired Web Marketing Today in 2012. In 2016, we merged the two sites, leaving Practical Ecommerce as the successor.

Most of us have had at least one experience of losing something in the postal mail. Hopefully yours was something small, like a postcard, not something like a mortgage payment or a rent check.

But despite how much we all complain about the post office, its delivery rates positively sparkle compared to email messages. Just last week, Return Path, the email certification service, reported that one in six emails never makes it to the inbox.

One in six is a lot. What if one in six of your customer-service emails went missing, or one in six order confirmations? Even with all the other demands on your time, to track sales, to create more content, to manage your social media accounts, when one in six of your email messages is getting lost, it’s time to do something about it. Just cutting that rate in half, from one in six to one in twelve, will give your entire email marketing program a 10 percent lift.

One in six is a lot. What if one in six of your customer-service emails went missing, or one in six order confirmations?

The good news is it’s not all that hard to improve deliverability rates. And, if your deliverability rates are already good, it’s not too hard to preserve them. Here are 21 simple techniques for increasing your list’s deliverability rates, or for keeping the healthy deliverability rates you’ve got. And there’s enough time before the holiday rush to see results if you make these changes now.

1. Use Double Opt-in, Not Single Opt-in

The difference between double and single opt-in is that with double opt-in (also called “confirmed opt-in”), people get a confirmation email after they’ve entered their email address into your form and clicked submit. They’re not subscribed until they click a link in the confirmation email.

Deliverability rates for lists that use double opt-in are significantly higher than for single opt-in lists. Their unsubscribe rates are also lower, and their open and click through rates are higher. Double opt-in crushes single opt-in on just about every metric, with one exception — you’ll get about 20 percent fewer subscribers on the front end with double opt-in. However, that small loss up front will translate into big rewards long term. Use double opt-in.

2. Purge Hard Bounces after One Bounce

A hard bounce is when an email message is sent to an email account that is closed or no longer exists. The major ISPs (Gmail, Yahoo, Hotmail) keep track of these bounces, and will start to suppress delivery of all your emails if you trigger too many hard bounces. So keep your list up to date and remove hard bounces fast. Most email service providers make this easy.

3. Purge Soft Bounces after Multiple Attempts

Soft bounces occur when an email message is sent to an email account that is full, or temporarily unavailable for some reason — the server is down, for example. Soft bounces are less of a problem than hard bounces, but it’s still a good idea to clean them up. After 3 to 4 soft bounces to an email address, it’s time to take it off your list.

4. Avoid Over-mailing

One marketer’s definition of over-mailing can be another’s everyday practice. But generally, if you’re mailing more than once a day, you may be over-mailing. Over-mailing is also a little trickier to blame for poor deliverability rates, because when you send more emails, people tend to respond less — i.e., you can’t just send twice as many emails and get twice as many responses. Those suppressed response rates can also contribute to reduced overall deliverability, which brings us to the next point.

5. Purge Subscribers Who Haven’t Opened or Clicked in Awhile

“Awhile” can be a year, or six months. Whatever time frame you pick is up to you, but you have to draw the line somewhere. If people aren’t opening or clicking on your emails, culling them from your list might hurt, but it will help the deliverability rates for the people you’ll keep.

6. Avoid Spam Traps

A spam trap is an email address that has not been used by a real person for a long time, like 18 months, and has since been taken over by an ISP or by an anti-spam organization. That email address is now called a spam trap because if any emails get sent to it, the sender will be flagged as a spammer. There are reports of a mailer sending just one email to a spam trap and having its Sender Score drop by 20 points. That’s a severe example, but it drives the point home: Mailing to even one spam trap can hurt you.

The top way to get a spam trap on your list is to buy an email list. But if you want to know some of the other, less common ways that even good email marketers can end up with spam traps on their lists, see “Email Spam Traps and How to Avoid Them,” my article on that topic.

7. Use a Consistent, Recognizable Sender Name and Email Address

In other words, don’t have your email messages be from a free email account (like Hotmail or Gmail). Use the name of your company or brand as the “from” name.

The image below shows why this is important. Your sender name is actually more prominent in some email clients that the email subject line is.

The sender name on your email messages is often just as visible as the email subject line.

The sender name on your email messages is often just as visible as the email subject line.

8. Send from a Consistent IP Address with a Good Sender Score

Not sure if you’re doing this? Ask your email service provider.

9. Use Clear Email Subject Lines

“Deceptive” is the term the ISPs use, when subject lines are intentionally misleading. It can sound a little harsh, but here are some examples of what they mean: Don’t mention a sale or a coupon in the email subject line and then not offer it in the email. Basically, don’t promise anything in the subject line that your email doesn’t back up.

10. Do Not Include Attachments

Never, ever include an attachment for the emails you send to subscribers. Got a PDF or some other file you want them to have? Include a link to download it in the email.

11. Do Not Use Fancy Coding Languages

Avoid Dynamic HTML, frames, PHP, JavaScript, Java, ActiveX, ASP, and “cache busters.” Just keep it simple, okay?

12. Avoid Known Spam Words

This is actually far more complicated than it sounds. Search on Google for “spam word lists” and look around. If you removed every word that appears on every spam word list from your emails, you’d have to communicate by images — there wouldn’t be any words left. That said, if you have to use a few spam words (and you will) try to use them as little as possible. For example, don’t open your email with “FREE FREE FREE FREE.”

13. Avoid Embedded Videos

This is too bad, because videos increase email engagement by a lot. But unfortunately, they can also suppress deliverability. If you still want to send something like a video, send an image that looks like a video, and link it to a page that automatically plays the video. Most of your subscribers won’t notice the difference.

14. Keep Message Size to 40KB or Less

That doesn’t mean you can’t ever send an email over 40KB, but try to keep most of your emails under that size. This may mean you have to take an extra step and reduce the size of any images in your email. It is extra work, but it’s worth it.

15. Use a Spam Screening Tool

Almost every email service provider will have one of these tools built into the interface where you create your emails, but if they don’t, head over to or any one of the free spam tools, and run your email through their process. It takes less than 5 minutes. To ensure a good deliverability rate, your email should have a SpamAssassin spam score of less than 5.0. If your email rates higher than that, the tool will definitely let you know.


Your email service provider most likely has a spam score tool embedded in it’s interface, but if it doesn't, use one of the free online tools, such as SpamScoreChecker, to make sure your SpamAssassin spam score is less than 5.0.

Your email service provider most likely has a spam score tool embedded in it’s interface, but if it doesn’t, use one of the free online tools, such as SpamScoreChecker, to make sure your SpamAssassin spam score is less than 5.0.

16. Use a Professional Email Service Provider

Do not mass email your subscribers from a personal email account. Do not use a WordPress plugin to manage your email list. There are dozens, if not hundreds of email service providers to choose from (MailChimp, AWeber and Constant Contact are some of the better-known ones). They all offer free trials or low-cost plans. Get one.

17. Avoid Purchased Lists, and Avoid Email Service Providers That Allow Them

Purchased lists can be very dangerous to deliverability rates of everyone else who uses the email provider. That’s why reputable email providers don’t allow their customers to use purchased lists.

18. Instantly Process Unsubscribes

While there are still email lists that will mail to their subscribers up to a week after someone has unsubscribed (such as political groups), don’t let that be you. Make sure people are immediately unsubscribed when they ask to be taken off your list.

19. Make Sure your Email Service Provider Has a ‘Very High’ SenderScore

If you’re not sure about this, ask your email service provider. If it’s good, it will be delighted to tell you how high its SenderScore is.

20. Use Advanced Anti-spam Technology

I’ll spare you the tech-speak of how these work. Just ask your email service provider if it uses DKIM (Domain Name System validation) and SPF (Sender Policy Framework). Hopefully, it does.

21. Be CANSPAM Compliant

Make sure your email service provider participates in industry initiatives like EEC, MAAWG, and ESPC, and feedback loop programs, and is CANSPAM complaint. It’s actually illegal to not be CANSPAM complaint, so your provider sure had better say yes if you ask it.

For the other initiatives, it’s not the end of world if your email service provider isn’t participating in all of them. What you’re looking for is evidence that the people sending your emails are actively in the fight against spam, and have good relationships with the major ISPs and anti-spam organizations. Again, just ask your email service provider if it is participating in these things.

Pamella Neely
Pamella Neely
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