Email Delivery


SparkPost, SendGrid, MailChimp / Mandrill, Mailgun, Aweber, GetResponse and ConstantContact
ElasticMail, mailjet, mandrill, mailgun, postmastery, socketlabs, GreenArrow

How to manage mail server and keep it off blacklists

Email Deliver Services:

Is there web-based tool for checking spam score?

To check if your server is being blacklisted:


  1. If you're using HTML emails, include a text part in the email as well (for recipients and anti-spam checkers), and keep that text as close to the HTML copy as much as possible. Always include plain text: “personal” e-mail messages, even if written using HTML format, always include a plain text part. If a plain text part is missing, most antispam filters become suspicious.
  2. Use a web-based tool to check your spam score when you design your email template.
  3. Make sure that we have a date header.
  4. Use a well performing, well administered and trusted SMTP server. See How to manage mail server and keep it off blacklists
  5. Need a tool / library for generating plain text version from HTML
  6. Keep your message's layout as simple as possible.
  7. If you are sending HTML emails, use high quality HTML emails. Don't use tools which generate horrendous HTML (example: MS Word). They often leave signs behind (like empty tags, etc), which are generally found in spam. Unbalanced tags and invalid tags will also flag an email as spam. If you use a title, make sure it is meaningful. The default titles generated by HTML tools are often used as spam sign.
  8. Don't use active components (JavaScript, ActiveX, plug-ins) in your email.
  9. Don't insert too much graphic. Write, don’t paint: most of your message must be text; avoid including large images. Once again, antispam filters become suspicious when the image / text ratio is too high.
  10. Do not use invisible web-bug to track your emails. If you must track your emails, use visible graphic.
  11. Avoid attaching files
  12. Avoid useless or needless encodings. Don't use base64 encoded text unless you need to.
  13. Don't include a disclaimer that your email isn't spam. Don't claim compliance with some legal criteria, especially one which is not actually law in your country. Only spam needs to claim compliance. Non-spam is supposed to already be in compliance.
  14. Use normal conversational language. Do not use excessive spacing, or capitalization. Do not use cute spelling. Do not s.p.a.c.e out your words. Don't put str@nge |etters 0r characters into your emails.
  15. Make sure that your privacy policy, including enforcement, and contact information, is easily found and clearly stated on your web site. It is good to include this information (where to find this policy, contact information), in your email. People who need to find out whether you are spammer will often look for this information. This will help you in staying out of blacklists.
  16. Be careful where you advertise, and which advertisements you carry. If you advertise with companies that send out spam, your domain will be flagged as related to spam. If you carry advertisements for those who spam, your domains will be flagged as being related to spam.
  17. Be careful which domains / companies you allow to advertise in your emails (if any). Allowing spammers to advertise in your email will get your emails flagged by the URI blacklist. On the other hand, don't advertise your domains with spammers. Having your domain name listed in their spams can also get you flagged by some URI blacklist.
  18. Avoid using spammy phrases like "Click here" or "Once in a lifetime opportunity"
  19. Avoid excessive exclamation points!!!!!!
  20. Avoid using all caps
  21. Avoid cxcessive font coloring such as bright red, or green.
  22. Avoid starting subject with Free, GUARANTEED, Buy, dollar sign ($) or (money) amount, etc.
  23. Avoid sending nothing but one big image (with little or no text) in the message
  24. Avoid designing HTML email in Microsoft Word, and exporting the code to HTML** (that code is sloppy, and spam filters hate it).
  25. Avoid having three or more CAPITALIZED words in the Subject line or has no subject line.
  26. Avoid attempts to disguise words within the email.
  27. Avoid invisible text. (Colour is the same as the background)
  28. Avoid using the word "Test" in the subject line
  29. Avoid sending a test to multiple recipients within the same company (that company's email firewall can only assume it's a spam attack)
  30. Be honest in your headers. Be accurate in who you are (From), and which systems the email goes through, preferably from your own servers, using your own domain name. Make sure the the To header indicates the recipient. If the recipient is a list or a class of people, state so. Don't insert strange Received headers, or any other unwarranted header. Spammers need to try to fake out filters by hiding their source and destination; if you try to hide your source and destination you'll look like spam too. Likewise, spammers often try to track their spam and guage its effectiveness through tracking headers they add to emails. If you add unnecessary headers to your emails, this can make them look like spam.
  31. Use a domain name which is identified by a verifiable IP address. Make sure that if someone checks on the domain of your From address and Reply-To address that these addresses are valid, and the machine that would receive any Reply email can be identified.
  32. Using SPF identification for your domain helps. It won't flag you as a good guy directly, but it will prevent bad guys from successfully masquerading as you.
  33. Use an intelligent message id which ties correctly to your system. Use an intelligent mailing agent, one which identifies itself in the headers and which isn't heavily used by spammers. Make sure your date header is correctly formatted and in the correct time zone.
  34. Be visible and public in your domain and hosting registrations. If people who check for you to see whether you might be a spammer, or to complain/ask about your emails, finds bogus entries in your registrations, or "private" or "hidden" annotations, that strongly suggests you are a spammer, hiding from an outraged public. If you are open about who you are in your registration emails, you'll get some complains and some queries. Answer those honestly and fully, and you should stay out of blacklists.
  35. Make sure you have active and monitored abuse <at> and postmaster <at> addresses. Register them with
  36. An email is only ever opened when the user decides to open it, and often they’ll make that decision based on the subject line. Crafting an appealing and informative subject line is the first step in a successful design. We’re unable to make any visual design changes to a subject line, but as designers we should be involved in ensuring that it represents what’s in the email, and that it’s recognizable and helpful. If the subject line fails in its job, your beautifully crafted design will never be seen. There’s plenty of information out there for help on improving subject lines, as well as research on what makes a subject line succeed or fail. Write a subject line that is informative (mention some of the topics), short (or at least has the most important information at the start), recognizable (so that it’s consistent with other emails from your client).
  37. For desktop email clients like Outlook and Apple Mail, the default preview pane is a tiny rectangle of space taking up less than 20% of the screen. It’s really important that the top of your email is informative. If all the reader can see is 300 pixels of your background color or an unrecognizable logo, they have to be really keen to bother reading on.
  38. Always check your email with images turned off. In some cases, embedding the images as MIME-encoded attachments can avoid the image blocking, which is worth knowing. However, sending images as attachments creates a greater risk of being filtered, slower download speeds, and more complex processes. And you can bet that if spammers start embedding all their images as attachments, the email clients will respond and start blocking those as well. The take-home message for us as email designers is that we cannot simply expect our readers to see the images. Added to that, many readers are unaware that images are missing or how to enable them, so they may just assume the email is meaningless or broken, and throw it out if it contains no content other than images. So what are we to do? Avoid images entirely? Well, you could, and in many cases a well-formatted HTML email without images can be highly effective and achieve all your goals. That’s not always true, though, and inevitably we’ll have clients or bosses who really do have valid requirements for images. The answer is to always design knowing that your images cannot be relied on. Make sure that if they don’t load, the email is still readable and recognizable. Does the email still have useful, readable content? Consider especially what the preview pane looks like when there are no images. Do you have visible text in the preview area?
  39. Keep email designs reasonably narrow. Your emails are probably being read in a very narrow window or frame. Most people don’t open emails in a full-screen window; instead, they scroll through a preview pane or viewing column that takes up only a portion of the screen. Added to that, consider the poor people using mobile email clients who at best have a few hundred pixels with which to work. Web surfers have overcome their fear of scrolling vertically, but horizontal scrolling is still rare. As a result, our email designs will generally be quite narrow, built to work in a limited screen space. Most commercial emails seem to be about 600 pixels wide at the most, which can feel almost claustrophobic when you are used to your 24-inch desktop monitor. This width restriction will naturally lead to certain design styles, such as restricting the number of columns and splitting the elements vertically more than horizontally.
  40. Most websites have headers and footers and contact pages, commercial emails tend to share a basic structure.
  41. Have Recognizable Sender Details. Studies on email open rates have found that trusting the sender is the single most important factor in whether an email is opened or not. That means it’s critical to choose an effective and consistent “From” name and email address. You need to choose a name or title that will be recognizable to your readers. Often that will be the company name, or perhaps the product or service people have signed up to learn about.
  42. The CAN-SPAM law requires that your emails must: have accurate “From” and “To” addresses, email headers, and routing information that identifies the sender, avoid deceptive or misleading subject lines, contain an unsubscribe or opt-out mechanism, identify itself as a commercial email and contain a valid physical address for the sender
  43. A person who knows it’s super easy to unsubscribe is far more likely to resubscribe later on if they need your information or services again.
  44. Adapting a Website Design into an Email Design. Making your email design feel like it’s from the same company—or website—is extremely important. If the email uses recognizable colors, titles, and imagery, the subject line and preview pane will remind the recipients about the sender of the email, providing the confidence to act. An email that’s visually disconnected from the site it links to will jar, even if it does convince some recipients to click a link. Don’t go crazy and try to replicate the entire website in an email, though. Your design should take the essential feel of the brand and translate it into what will work for an email.

There are several whitelisting services which lower scores for sites using SpamAssassin network tests. Return Path’s Sender Score Certified is an email accreditation program (or "whitelist") with strict standards for both infrastructure and practices. Return Path also operates the Sender Score Safelist, with somewhat different criteria. Given that, as a result, we can count on mails from these programs being non-spam, we're happy to give it "bonus points" and allow it through filters. provides a Whitelist of known legitimate email servers to reduce the chances of false positives while spam filtering.

ISPs see spam complaints less seriously than spam traps; still they can hurt your sender reputation. Spam complaints happen when the recipients of your emails click the “Reports as Spam” link, sending off a signal to their ISP that your email was not wanted or asked for.

FBL (Feedback Loop)s are not only help with list hygiene and deliverability but are an invaluable source of behavioral data. A feedback loop is a mechanism whereby an ISP will let you know when one of its subscribers complains about your e-mail. All the Big Four operate such loops (except Yahoo, who is still developing its), as do a number of other ISPs, including Road Runner, United Online, Excite, and Outblaze.

FBLs invariably require sender registration and may have other requirements. To scale more effectively, for example, AOL is moving toward requiring SPF records for its whitelist and FBL management. Once registered, when a recipient complains about your e-mail (by clicking the "this is spam" button or contacting the ISP's abuse desk), an e-mail is sent to the address you registered. The e-mail is typically in the MAAWG (Messaging Anti-Abuse Work Group) endorsed automated response format (ARF).

It's important to understand that though your list may be 100 percent opt-in, it may still receive a substantial number of FBL complaints. For years, end users have been told not to trust e-mail unsubscribe links, so many users hit the spam button as a way of unsubscribing. The result is complaint rates through FBLs can be much higher than a list's unsubscribe rate. To further complicate matters, most ISPs have complaint rate thresholds above which your messages may be filtered or blocked. Unfortunately, most don't publish these thresholds, which vary by ISP. AOL states mailers should aim for a complaint rate of 0.1 percent (1 complaint per 1,000 deliveries). That's a useful baseline.

Smart marketers use FBLs in two main ways. The first is for list hygiene: removing the subscriber from future mailings. Although some ISPs make responses anonymous (the recipient line is often erased), it's generally still possible to determine the original recipients and unsubscribe them. Some may call this list-washing, but it's just common sense. Even if someone previously opted in to receive messages, if he complains, the first thing you should do is cease mailing to him.

The second use of FBLs is to analyze the complaint rate. Too many marketers dismiss complainants as troublemakers and malcontents. The reality is there's a wealth of data in who complains and what they complain about. Regardless of whether you believe the complaints are unfounded, if they complained they were dissatisfied. Smart marketers aim to avoid dissatisfied customers (or prospective customers).

If a particular mailing, list, or list segment produces too many complaints, it bears further investigation. In my experience, the majority of complaints are caused by a failure to meet expectations. A common case is high complaint rates among new subscribers. This can be caused by subscribers not realizing what they signed up for, subscribers not getting what they thought they signed up for, or a long delay between sign-up and the first mailing.

By analyzing FBL data, such problems can be identified and solutions developed and tested. The net result is happier recipients, happier ISPs, improved deliverability, and better results. Make sure you're on the FBLs of all ISPs that offer them and that you're using the wealth of data those FBLs provide.

Do we need to include X-Anti-abuse header?
Do we need to include an SPF header?
What tool do we use to make sure that we stay off the blacklists?
Make sure that our email server is not listed as an open relay server
Make sure that our email server is not listed on any blacklist
How to improve email delivery?
How do spam filter work?

How to properly set up SPF, SenderID, DomainKeys and DKIM.
How to get whitelisted at AOL, Yahoo, MSN, and Hotmail.
What are FeedBack Loops and What Do They Means to You.
Your Email Reputation in 2008 and what it Means to Your Email Delivery.
What to do if you are blocked by SpamCop, Spamhaus of any of the ISPs
How to contact Blocking ISPs and What You Will NEED when You do call.
How to find out if my mail server is blacklisted?

How can you tell if your campaign ended up in recipients' junk folders? For starters, look at your open rate. If it suddenly dropped from your average, you probably have a spam filter problem. If you're new to email marketing, 20-30% is a rough open rate average.

An abnormally high bounce rate is another indicator. Look through your hard bounces, and read the SMTP replies. Spam filters sometimes leave little clues about why they blocked your campaign

Most established email marketing services (like MailChimp) have been accepted into feedback loops with ISPs like AOL, Netzero, MSN, Hotmail, and more. Whenever a recipient on their network reports an email as spam, an alert is sent to the sending server. MailChimp receives those alerts and stores them under your account, so you'll know how many people reported your campaign as spam (MailChimp will also remove those people from your list automatically, so you don't get reported again).

Never ever set the from-header to the users email adress! You may get blocked by spam filters due to SPF

Getting in the Feedback Loop
What is SPF!PAGETYPE?sq=bounceback%2bheaders&sf=101113&sg=0&st=497952&documentid=162494&action=view
HTML Email Validator

Checking Blacklisted IPs with Nagios
Checking Blacklisted MTAs with CentOS + check bl

PHP libraries for sending email:
RMail / HTMLMimeMail5

How do spam filter work
How to improve email delivery rate
How to prevent your email from going into spam / junk folder
How to avoid spam filter
How to manage email server (should cover aspect such as "how to keep email server from being blacklisted", "how to keep email server from being used as an open relay by spammer")

Who Sends HTML Email, Anyway?
Improve your email subject line
The Principles of HTML Email Design
We Know Where You Live - The Death Of Privacy Online

Having Trouble Sending Mail?
Email Standards Project
Mail Server Naming Problems
Reading Bounce Back Headers (SMTP Replies)


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