Best Practices For Bulletproof E-Mail Delivery

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Have your e-mails already been flagged as spam, although you’ve sent a seemingly legitimate proposal to your client? Have you ever wondered why the efficiency of your newsletter campaigns suddenly dropped down? In both cases you deal with a problem which is harder to get done with than you think it is: bulletproof e-mail delivery.

The main problem with undelivered mails is that both sides — sender and recipient — don’t really know what happened. Was the e-mail sent? Is the task done? Was the e-mail delivered? Most recipients will never know that an e-mail flagged as spam was sent to them — they just don’t receive the e-mail. And most senders will never know that an e-mail flagged as spam wasn’t delivered — they just don’t get a response.

This article suggests over 20 bulletproof techniques, best practices and related services you can use to ensure best e-mail and newsletter delivery rates.

Where Do We Stand?

E-mail is a primarily mean of communication in the Web. Instant messaging supplements e-mail, however it’s a choice when it comes to communication with people you know well and/or you have a regular contact with. So where do we stand? And what is the main problem with e-mail delivery? And why do we have to deal with it?

  1. Spam-filters calculate “spam score” to detect junk mail.
    To determine whether a given e-mail is spam or not most spam filters consider a number of different attributes, such as content, length, percentage of text, use of images, number of recipients, headers etc. Usually they calculate the so-called “spam score” for every e-mail which passes the server.

    If the mail’s score exceeds a certain threshold the mail is blocked and lands in the spam folder. The level where the threshold is set is defined by the mail server configuration. By default, this spam filter flags messages with a score greater than 5 as spam.

  2. Spam filters aren’t perfect.
    Over the last years the efficiency of spam filters used by e-mail software clients and web-based e-mail-services has improved dramatically. However, since the strength level of anti-spam-algorithms has increased, it’s inevitable that also more legitimate e-mails don’t get through them. The result is that these filters, in order to block a good percentage of spam mails, block a good percentage of “suspicious” — in reality non-spam — messages as well.
  3. Newsletters remain important, RSS-feeds haven’t made the breakthrough yet.
    In its recent usability study Nielsen Norman Group found out1 that news feeds are definitely not for everybody, and they’re not a replacement for email newsletters. Apparently, “feeds are a cold medium in comparison with email newsletters. Feeds don’t form the same relationship between company and customers that a good newsletter can build.

    [..] Given that newsletters are a warmer and much more powerful medium, it is probably best for most companies to encourage newsletter subscriptions and promote them over feeds on their website.” Therefore it’s important to be aware of some sound techniques to pass through anti-spam-filters and thus guarantee a good newsletter delivery.

  4. E-mail delivery is tricky.
    The fact is that in most cases you never really know whether your first e-mail adressed to someone who doesn’t know you and/or isn’t expecting your e-mail will come through mail filters. And since the recipient doesn’t expect your mail he/she won’t be able to take it into consideration. Therefore it’s necessary to be aware of some techniques to ensure the delivery of your e-mails.

Best Practices For E-Mail Delivery

According to latest studies, your reputation determines your email delivery more than your content2. So if you meet the expectations of your readers / recipients and don’t send irrelevant information you improve the delivery rates of your e-mails. Apparently, “most delivery challenges are due to subscriber feedback; such feedback typically takes the form of complaints by recipients who mark the message as “spam” in their respective email clients and problematic traffic patterns such as bounces and spam trap hits.”

However, it’s not always enough. Let’s take a look at the best practices for optimal e-mail delivery rates.

  1. Avoid follow-ups, ask for a brief feedback — one word “soon” is enough.
    Since you don’t know whether your e-mail is delivered or not, don’t assume that it is delivered. However, don’t send a follow-up in doubt; follow-ups which usually include the copy of an original e-mail aren’t effective and get on recipients’ nerves. Instead ask the recipient in the first message to send you a brief note that your e-mail was received. For instance, ask to write back “soon”, “got it” etc. once they’ve received the e-mail — indicate that no further comment or instant reply to your mail is necessary.
  2. Don’t attach large files to your first e-mail (unless specified by the employer).
    Instead provide the detailed information on where the your CV and portfolio can be found on your personal web-site. Or simply copy and paste your resume in your e-mail. Compressed files (.zip, .tar etc.) and images are still strong signals for spam detection algorithms.
  3. Use a consistent senders’ name and email.
    Make it easier for your recipient to recognize you. Don’t change from “Max Mutermann” to “Developer’s team”. Don’t change your e-mail suddenly. Once your recipient has mistakenly considered and reported your message as spam you are likely to never be able to contact them again.
  4. Never put a link before important information.
    Once the recipient has clicked upon the link you’ve provided and landed on some page he/she has no information about, you’re lost. Many recipients might not get back to your message and report you as spam.
  5. Snail mail is bulletproof.
    If possible, follow-up on your e-mail with a “snail mail” version sent to the real postal address. This is a great way to establish contact and stay in touch with a person! Reference the e-mailed version you sent (including the date, time, and subject if possible). [Source3]
  6. Avoid fictional or irrelevant sender’s name.
    Communicate with your recipient personally. Instead of nicknames or company titles use your first and last name. Notice that spam-filters award e-mails without sender’s name (or with an empty name) with spam score points. The sender’s name shouldn’t include numbers or symbols rather than your actual name. Instead of “no-reply@yourdomain” or “admin@yourdomain” provide your readers with concrete and short contact information, e.g. “Max Mustermann” . The “reply-to” field shouldn’t be empty.

Best Principles For Bulletproof Newsletter Delivery

Since newsletters are still an important part of marketing campaigns, to achieve the highest response rate you’d like to ensure the highest delivery rate. The principles and rules listed below might help you to increase the delivery rate of your newsletters.

  1. Send newsletters regularly.
    Let your subscribers know when your emails are coming. If you offer a subscription to your newsletter from your web site then tell each and every subscriber exactly when to expect your newsletter. [Source4]
  2. Tuesday / Wednesday 2-3pm = Increased Response.
    Your subscribers will come to “expect” your email to arrive in their inbox on the same day at the same time every week, meaning that they want to read your content and are generally more receptive to any special offers or promotions you may include. This means that they are less likely to misunderstand your newsletter and report it as spam. [Source95]
  3. Slow down your newsletter delivery.
    Instead of using tools which boost your newsletter through mail servers to achieve “instant delivery” prefer “slow” delivery tools. Avoid sending mails to multiple (dozens or even hundreds) recipients using CC:-attribute. Use professional newsletter software or professional e-mail-delivery services. “When ISPs detect a flood of email, it looks like the work of a virus or a spammer.” [Source6]
  4. Use a tag line at the beginning of the subject line.
    Mark your newsletters as such. Make it easier for your readers to recognize your newsletter. E.g. ‘[SM Newsletter] Nr. 297, 16.10.2007 — Usability Glossary — Splash Pages — Big Typography’. Remain consistent. Otherwise your readers might consider your e-mails as spam and report it. [Source7]
  5. Always insert the current date in the content.
    A correct date which indicates when the newsletter was sent is more important than you probably think it is. If the date isn’t mentioned or is provided incorrectly, the newsletter is given spam score points.
  6. HTML is OK, but only if MIME-Multipart is used.
    When sending newsletters as HTML make sure that also the plain text version is attached. Messages sent in MIME-Multipart-Format are automatically sent in a way that subscribers without active HTML-Viewer still get a decently formatted e-mail. It is important that both plain text and the HTML-version have the same or very similar content. The percentage of text should be higher than the percentage of HTML or images. Keep your message size between 20 and 40 Kb.
  7. Use CSS sparingly.
    In most cases it is better to use inline CSS-styling in HTML instead of referring to CSS-file in HTML. However, referring to external CSS-files is better than sending them with newsletter.
  8. Avoid graphics and complex HTML-elements.
    Spam-filters consider a number issues related to HTML. For instance, if the newsletter has too many closed tags, too many graphic (images) or structural (tables) elements it gets just as many spam score points. Besides, many readers use software (e.g. Outlook) which automatically blocks images; if users don’t understand what the mail is about they’ll report is as spam. Complex HTML (particularly if more than 50% of HTML-code are HTML-tags) is generously awarded with many spam score points — keep it simple. Colorful backgrounds, tables, JavaScripts and web forms shouldn’t be in newsletters.
  9. Motivate your users to add you to their whitelists.
    To ensure the bulletproof e-mail-delivery ask your readers to add you to whitelists. You can create Email whitelist instructions in seconds8 — for a number of e-mail applications.
  10. Screen your advertisers and partners.
    If your newsletter includes a link to a blacklisted web site you might get a whole bunch of spam score points. Verify the sites and e-mails you are linking to; check if they are already blacklisted or were reported as spam (or spam sources) before placing their advertisements in your newsletter. Even if the company is legitimate, it is possible that spammers have used their accounts for sending out spam mails.
  11. Monitor new subscribers.
    Monitor new subscribers in your lists. Set suspicious “spamflag” addresses such as “abuse@”, “nospam@”, “postmaster@”, “marketerspam@” as inactive subscribers. [Source]
  12. Verify your subscribers with signup confirmation.
    Always make your mailing lists double opt-in. This means that when a user subscribes to your mailing list, they will be sent an email with a link that they must click on to confirm their subscription. This is very important because many people can accidentally enter an incorrect email address, or even the email address of someone else on purpose. When that person receives a newsletter they did not subscribe to, they will assume they have been spammed, and your newsletter (and possibly your web server) will be reported as spam. [Source95]

    It also keeps invalid email addresses off of your list, which reduces the volume and percentage of undeliverable messages that you send. Since undeliverable rates also factor into filtering rules, keeping invalid email addresses from being subscribed to your list will help you to avoid content filtering. [Source10]

  13. Test your newsletters before sending them out.
    Always check the “spam score” of your newsletters with Free Content Checker11, SpamCheck12, Contactology2013 and further tools (most of them are listed below).

Tools and Services

Before sending the newsletter out you are likely to check whether your content will get through most spam-filters. Since spammers always come out with new ideas of tricking filters and filters are being updated all the time even absolutely innocent mails can land in the junk folder. Let’s take a look at some tools you can use to check your e-mails once they’re ready to be sent.

Spamcheck14 offers you the possibility to check your content via e-mail or through the Spamcheck online form.

Spamcheck15

Once you’ve provided the sender’s information, subject and the content of your e-mail, Spamcheck evaluates it rewarding the e-mail with spam score points and provides you with a SpamCheck Report. As most filters, many different aspects are taken into consideration; if your e-mail has 13 points or more you can be sure that it won’t find its way to your recipient’s inbox.

SpamAssassin Tests16 is the list of indicators currently implemented in SpamAssassin, the #1 Open-Source Spam Filter used on most Apache servers. This list describes the indicators and the spam score an e-mail gets if this aspect is found in the e-mail. A score higher than 5 points typically indicates that a message strongly resembles spam, and would possibly be blocked or filtered by major email providers or ISPs. You might need to time to understand what the indicators are and what you should do to minimize your spam credit. However, it’s worth it.

Spam Assassin17

Sparklist Content Checker18 runs a free test of your e-mail through Spamassassin and presents you a detailed “spam check”-report with possible “false signals”.

Content Checker19

Contactology2013 offers a spamcheck per web form. The Message Quality Score21 (MQS) used by Contactology allows you to quickly determine a message’s quality and deliverability on a scale from 0 (bad) to 100 (excellent). You can check the likelihood that the message will be blocked by spam filters given the content of the message and all the message headers and the likelihood that the message will look as intended in all mail readers.

Contactology22

Contactology23

In our test one of our e-mails had the score of 92. Not bad, but it can be improved.

Among commercial solutions you might want to check out Delivery Monitor24. Delivery Monitor is a powerful tool for gaining valuable, real-time information about your campaigns—are they being delivered at all and, if so, are they making it to recipients’ inboxes. Use Delivery Monitor to determine if your mail is automatically routed to “spam” or “bulk” folders at more than 50 different ISP’s and email providers, then take corrective steps to delivery more mail to the one place it will be read — the inbox. The tool provides real-time feedback about email deliverability, highlights delivery issues and indicates if deliverability problems arise during a campaign, so you can pause the mailing until the issues are resolved.

Lyris Delivery Monitor25

Mailchimp Inbox Inspector26 is an optional add-on to MailChimp27 account that allows you to check your email marketing campaigns instantly. It generates the screenshots of a sample promotional email, rendered in 16 different email programs, points out problems with spam filters and corporate email firewalls as well as broken links and typos.

Screenshot28

Campaign Monitor29 is built for designers who can create great looking emails for themselves and their clients, but need software to send each campaign, track the results and manage their subscribers. You can see screenshots of exactly how your email will look in more than 15 of the most popular email clients like Outlook 2007, Windows Live Hotmail, Yahoo, Gmail, Lotus Notes etc. Instead of scanning your content for “spammy words”, the tool passes emails through real spam filters and tells you exactly why you failed. The e-mail is also run through a number of key spam firewalls – the gatekeepers for most ISP’s and large corporations.

Screenshot30

The tool also provides a comprehensive set of real-time reports allowing you to accurately measure the effectiveness of every campaign you send.

Screenshot31

References, Sources

Footnotes

  1. 1 http://www.nngroup.com/reports/newsletters/summary.html
  2. 2 http://www.lyris.com/news/pr/pr-052907.html
  3. 3 http://www.job-hunt.org/article_antispam.shtml
  4. 4 http://www.interspire.com/content/articles/52/1/Improve-Your-Email-Delivery-Rates
  5. 5 http://www.interspire.com/content/articles/6/1/Avoiding-the-Spam-Filters-and-Other-Email-Marketing-Tips
  6. 6 http://www.imediaconnection.com/content/6806.asp
  7. 7 http://www.keywebdata.com/?page_id=16
  8. 8 http://www.keywebdata.com/?page_id=28
  9. 9 http://www.interspire.com/content/articles/6/1/Avoiding-the-Spam-Filters-and-Other-Email-Marketing-Tips
  10. 10 http://www.aweber.com/blog/email-deliverability/isp-content-filtering.htm
  11. 11 http://www.sparklist.com/resources/tools/contentchecker/index.html
  12. 12 http://spamcheck.sitesell.com
  13. 13 http://www.contactology.com/check_mqs.php
  14. 14 http://spamcheck.sitesell.com
  15. 15 http://spamcheck.sitesell.com
  16. 16 http://spamassassin.apache.org/tests.html
  17. 17 http://spamassassin.apache.org/tests.html
  18. 18 http://www.sparklist.com/resources/tools/contentchecker/index.html
  19. 19 http://www.sparklist.com/resources/tools/contentchecker/index.html
  20. 20 http://www.contactology.com/check_mqs.php
  21. 21 http://www.contactology.com/mqs.php
  22. 22 http://www.contactology.com/check_mqs.php
  23. 23 http://www.contactology.com/check_mqs.php
  24. 24 http://www.lyris.com/products/emailadvisor/delivery_monitor.html
  25. 25 http://www.lyris.com/products/emailadvisor/delivery_monitor.html
  26. 26 http://www.mailchimp.com/add-ons/inboxinspector/
  27. 27 http://www.mailchimp.com/index.phtml
  28. 28 http://www.mailchimp.com/add-ons/inboxinspector/
  29. 29 http://campaignmonitor.com/
  30. 30 http://campaignmonitor.com/
  31. 31 http://campaignmonitor.com/
  32. 32 http://www.anandgraves.com/html-email-guide
  33. 33
  34. 34 http://www.emaillabs.com/email_marketing_articles/html_email_design_tips.html
  35. 35 http://www.keywebdata.com/?page_id=16
  36. 36 http://www.wired.com/techbiz/it/news/2004/01/61945
  37. 37 http://www.imediaconnection.com/content/6806.asp
  38. 38 http://www.newsletterarchive.org/faq.php
  39. 39 http://www.keywebdata.com/?p=32
  40. 40 http://www.mailchimp.com/resources/html_email_mistakes.phtml
  41. 41 http://www.wordbiz.com/avoidspamfilters.html

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Vitaly Friedman loves beautiful content and doesn’t like to give in easily. Vitaly is writer, speaker, author and editor-in-chief of Smashing Magazine. He runs responsive Web design workshops and loves solving complex problems in large companies. Get in touch.

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  1. 1

    Nice to know!

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    • 2

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  2. 3

    Very good post – thank you. I work at a company where we send about 1.5 million emails / week (all legitimate and to our customers). I will have a proper read through tomorrow and see if there is anything we can improve upon.

    Thanks again!

    0
  3. 4

    Good and complete research :). Thanks.

    0
  4. 5

    This is excellent information. I have bookmarked it and will use it when I send my promotional emails/newsletters.

    You guys rock!!

    0
  5. 6

    Thank you very much for this great post! Very usefull information because its a real problem. Just one of the plenty problems we have because of spam…

    0
  6. 7

    Hi, This article is suitable for websites. you gonna tall me it is the aim of your website and I fully agree. The thing in that I work in tech support. My main clients are the most know brands in the PC world (software developers, PC manufaturers, PDA,…) and the driver for customer dissatifaction is spam filters. customers are raising support requests on our web forms and when we reply our mails are rejected by spam filters.
    This article is very interesting and everything is true but a deeper analysis of the way spam filters calculate the “spam score” would have been an useful plus to this article.

    Anyway thanks for all your articles… and I do use your RSS feed whatever you state about feeds ;)

    1
  7. 8

    What about images? A good technique consists in embedding them.
    I’d like to know how often I must send the newsletter ? Is once a month ok ?

    Now i’m gonna test the tools. Thanx Smashing !

    0
  8. 9

    This is a good post. But I think the new site design royally sucks – mainly the ads that are all over the place. Put them on the sidebar, or in the header, and not in the middle of content. This is design 101…

    0
  9. 10

    Really a great article!

    With the growth of the anti-spam solutions, it’s sometimes hard to get the mail where you want it to go. Thanks!

    1
  10. 11

    Erm. I agree. The new web design sucks.

    0
  11. 12

    Thanks for this timely article. Just what I needed to know.

    0
  12. 13

    Does anyone know a good Newsletter delivery service in German? Most of them seem to come from the States, where they are supremely language-challenged, and a newsletter that is half English, half German is just not right.

    Kennt jemand von euch einen guten Newsletter Lieferdienst in Deutsch? Da wir unsere News in Deutsch verfassen, sollte auch das Newsletter Rahmenwerk in Deutsch sein. Wäre für jeden Tipp dankbar. Bitte an helmar@ senden oder hier kommentieren. Danke!

    0
  13. 14

    Helmar,

    I’m from Mallorca, working in a german company and have used a newsletter tool from a compay called Dievision.

    It’s not very flexible in some ways and very flexible in some others, but they are Berlin and Hannover based, so talk to them and see what they can offer you!

    You may have to use some other service from the article, like the spam checker and so, but do the delivery with them, they are very responsive.

    Hope this helps! Cheers!

    0
  14. 15

    Nice, i just checked a marketing email for my agency and scored: 1.4 (out of 13) … another thing to boast about @_@

    0
  15. 16

    Wow that is really very informative! Thanks for spending your time again to get such a great article done for the good of others. Now its time to put those tips into practice. =)

    Swift

    0
  16. 17

    This article is a little behind the times. All these things are good to do, and very basic, but there is a bigger issue of sender reputation and there isn’t anything on here about CAN-SPAM requirements which are essential.

    Its a good article if you’re a novice. Also seems to be sponsored by Lyris whose deliverability package isn’t exactly top notch.

    1
  17. 18

    http://litmusapp.com is the best e-mail design checker I’ve ever seen, definitely worth an inclusion.

    0
  18. 19

    the ads are ‘all over the place’ so that you cannot ignore them as you would if you had them in one place :)

    If they ads are auto ignored then you wont click and the revenue will be less…you should use ADBLock or selectively block Javascript to stop the loading of the adverts..

    to the article, interesting reading, however it didnt address the potential of your mail system being used against you, to attack your site! think about it, restrict the ability of bots and others to solicit mail from your site!

    1
  19. 20

    I’m surprised this post didn’t have anything on bounce management.

    1
  20. 21

    I haven’t used Lyris in about a year or so, but when I did, I found it to be one of the worst usable sites for sending out email campaigns, even if the funcionality is there, it was painful to send out campaigns.

    it might be an unfair comparison, BUT campaign monitor has been like breath of fresh air.

    if anyone has used Lyris, would like to hear about your experience, good or bad..

    0
  21. 22

    Appreciate the useful information. Thanks for helping us get our newsletters delivered more often. – Scott (ARRiiVE.com and

    0
  22. 23

    Enjoyed the article. Can I second Darren’s comment about bounce management, though.

    One of the quickest ways to get on blocklists is to keep sending email to dead addresses. So it makes sense to look at the bounced emails you get.

    Those addresses that are dead need to get taken off your list. And those that have temporary delivery problems (account storage full or timed out etc.) need to be monitored. If they keep bouncing, take them off the list, too.

    Also, MailChimp just updated Inbox Inspector to give more screenshot options. For example, more screenshots of displays when images are blocked etc. (For the record, I’m not affiliated with the company, just familiar with the tool!)

    0
  23. 24

    Agust Gudbjornsson

    November 24, 2007 9:17 am

    Well nice, BUT its more simple just to create your own “keyword” filter system.

    We tried allot of different elements for our server and they where mostly to -static- so to speak.

    Today we block 90% or more of our incoming spam by using manually made keyword filter system, which also shows us how many mails we have blocked and how many have gone though. Also including Quarantine system which shows us before its deleted within 5 days. On top of that we have error message to any sender if they are added into the quarantine for mistake (never happened so far)..

    so for any of you who run servers, I would say its best to generate special keyword filter for your server in your admin systems..

    If you have interest we can share interests on this. Just send me few lines.

    Great article though guys! Well appreciated work that you do here in this great site!

    0
  24. 25

    Thanks again for another excellent article – the tools are very useful. This site is my most valuable development resouce.

    I agree that addressing bounce back management would be useful.

    0
  25. 26

    great article. I used to work for an email marketing company. I used to advice the clients of most of these points and still some of them didn’t bother listening to me. They say the customer is always right but no no no, they’re not. Thanks again for this great article. Keep up the good work.

    0
  26. 27

    Great article and a big thanks to the folks making whitelist instructions generators available! (emaildeliveryjedi and cleanmymail ).

    It really helps but I’m looking for something more. I’m looking for a service that can keep our whitelist instructions up to date (RSS feed? ) and or provide screenshots along with the instructions. ( Helps with less computer savvy folks… which of course are the people that have the trouble.

    Its a long shot…. but would be a service that would be well worth paying for. Any leads would help. Cheers!

    0
  27. 28

    I am new to SmashingMagazine.com and I realize that this article is older, so I don’t know if you have fixed the problem in more recent posts, but: as a fan of online media and a proponent for sites that aim to make the internet a place for true journalism and editorials I am a little upset by the editing of this article. I haven’t even gotten half way through the article and I am annoyed by the grammatical errors. There were dozens of sentences started with “And”, paragraphs that had little direction, and words that were outright misspelled. Now, this is fine on a blog, or in comments, but as a supposed “magazine” I expected better. Am I nitpicking? Probably. I still hope that the editing chops of the Smashing team will get (or have already gotten) better.

    0
  28. 29

    Excuse me, the word I thought was misspelled was not: I was unfamiliar with the British spelling.

    0
  29. 30

    The style of writing is quite familiar . Have you written guest posts for other blogs?
    p.s. Year One is already on the Internet and you can watch it for free.

    0
  30. 31

    Great article, but I’d love to see something on HTML email design. I’d even take a showcase of nice looking emails from design firms. Please?

    0
  31. 32

    This article is good but it is leaving out some really important information such as reverse dns, proper spf records, domain keys / dkim… , Feedback Loops and Requests for whitelist.

    0
  32. 33

    I did not know a sharing feature on this post that would easily allow me to Email this post.

    0
  33. 34

    This is very good – I try to keep images to a minimum, but sometimes, an image or two is needed. When I get a html email, I do turn on images if I recognise the sender, or if something catches my interest. I was just wondering, does anyone know statistically how likely recipients are to turn on images?

    0
  34. 35

    wow this is really helpful! thx!!

    0
  35. 36

    Nice article – an in depth take on the issue that drives all email marketers crazy.
    Particularly liked your piece on the bullet proof email deliverability, it reminded of me about an article on double opt in benefits…

    http://www.pure360.com/email-marketing-blog/blog-entries/optimise-your-email-marketing-with-double-optin

    0

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