Diagnosing your Deliverability Problems


Mystery of the Missing Email

Sometimes it can seem like quite a challenge to figure out why your email isn’t getting delivered. A few spam blockers will kick out reasons (like Postini and SpamAssassin), but many others won’t give you any information at all. So how can you figure out what problem is plaguing your latest email campaign? It’s not as difficult as you might think. The tools we offer at Email on Acid can make it easy to determine the problem.

Deliverability problems fall into one of the following categories:

  1. Email Server/Address Reputation
  2. Email Server Configuration
  3. Email Content or Subject Line
  4. IP Address Reputation

Email Server/Address Reputation

Spam filters make lists of suspicious email addresses and IP addresses based on emails it has previously filtered. If other people using the same ESP as you are sending spam, or if somebody who previously used that IP address sent spam, your email could be seen as more suspicious by spam filters.

Testing the Sender Email Address

To test the sender email address try using our Spam Test SPAM testing puzzle tool using a different sender address. If the same email gets to more inboxes with a different sender email address, that could be your problem. It’s best to use a from address that recipients can reply to, that has a recognizable name attached to it (e.g. “Super Electronics, newsletter@superelectronics.com). Remember to keep other variables the same. For instance, if you are experiencing deliverability problems by sending via your SMTP server, change ONLY the sending email address and try your spam test again.

Email Server Configuration

It could be that nothing is wrong with your email content or reputation. Server configuration issues can also cause problems with outgoing mail. Perhaps emails aren’t even being sent out from your server due to a configuration error. Our Spam Test tool is capable of detecting many email server configuration errors and advising you about them so that they can be resolved.

Email Content or Subject Line

This may seem like a broad category, but checking over your subject line and content should be fairly straightforward. Both of these things are probably much more under your control than the reputation of your IP address. Check for the following top problems with content and subject line.

  • ALL CAPS – Spammers love to use capital letters to get attention. To bad for them it gets the wrong kind of attention.
  • The Word “Free” – Especially in subject lines, this word should be avoided.
  • Bad HTML – Be careful with your HTML. Run it through a validator (like ours) and make sure you don’t have any empty tags (like ““) or unclosed tags. Spammers often have messy or poorly written HTML and spam filters will take notice.
  • Avoid IP Address Links – Another tactic used by spammers, IP links should be avoided in favor of regular URLs. If the reader can tell where the link goes, so can the spam filter, and that’s good.
  • Include Opt-Out Options – Including items like this legitimizes your email by providing an easy way for recipients to unsubscribe. It also helps maintain your reputation by reducing the number of recipients who use their email client to flag your email as spam. If you don’t provide this option, many users will flag your email as spam just to try and make sure they don’t get another one.

Testing the Content or Subject Line

To test the Email Subject Line try changing the subject line and resending the email. Remove any words or phrases that might seem spammy and remember that testing this is a trial and error process. If removing all questionable content from the subject line doesn’t help, start looking at the content. Try removing/changing one questionable element at a time and resending to identify the problem.

IP Address Reputation

If the IP address that you’re sending from has been associated with spam in some way, it may be flagged by the filters. Before checking the content of the email, the IP address is checked to see if it is white or blocklisted. If you’ve been whitelisted, your email will go through without its content being checked at all. If it has been blocklisted, the email will be “black holed,” bounced or flagged as spam without the content being checked. Black holed emails are not delivered to the user, but are secured in a place accessible to administrators in case they are needed later. This approach is often used for emails that contain viruses, to keep end users from opening them on accident.

Testing the IP Address Reputation

To test the IP Address Reputation try sending your email through the Email on Acid servers. If an email was not delivered when sent through your servers but is delivered with no problems through ours, you may have a server reputation problem. If it still isn’t delivered when using our servers, you may have a problem with one of the other categories listed above (Sender Email Address Reputation, Server Configuration or Subject & Content.)

Author: Alex Ilhan

Hailing all the way from England, Alex brings his email development expertise along with an endless stream of cups of tea and British cynicism. Follow him on Twitter: @omgitsonlyalex.

Author: Alex Ilhan

Hailing all the way from England, Alex brings his email development expertise along with an endless stream of cups of tea and British cynicism. Follow him on Twitter: @omgitsonlyalex.