Spam Triggers

Spam is a large problem on the Internet and can lead to mail servers becoming blocked for future sending. This is especially painful in a shared environment, because one spammer can affect many innocent users. It is our responsibility as a mail service provider to take measures to prevent spam from originating on our systems. While it is in everyone’s best interest to stop spam, we do not want to inconvenience legitimate users who may have inadvertently triggered our scanners. To determine why your email attempt resulted in this error, and to prevent future emails from being blocked, please have a look at the below possible reasons for the mail being blocked.

Mail subject and body content

By far the biggest triggers of spam for everyday mail is the subject and body text of your mail, spam filters are very sensitive to message content and its advised to try and avoid the following words and phrases if at all possible.

HTML has a low text to image ratio

When screening HTML for red flags, spam filters examine the ratio of text to image. If an email contains either too many images or a large single image area relative to a small amount of actual text, points are added to the spam score, increasing the chances that the message will be blocked.

Links

Messages with links to external web pages are more likely to be identified as spam. It’s also advised to always use the fully qualified domain name instead of IP addresses ( http://example.com vs http://1.2.3.4 )

Sending server reputation

If your sending server has recently sent out a lot of spam, all messages coming from that server may be blocked, even if they are not spam. You can use a third-party website such as MX Toolbox to check your IP address against many different block lists at once. There are several free websites available for this kind of check.