Spam Rating

Why is my Message detected as Spam and how can I avoid it?

Today almost all mail boxes are protected by some kind of anti-spam filter. Client based filters are part of most mail clients and most anti-virus programs contain additional plug-ins for popular mail clients like e.g. MS Outlook. Server based filters can move a message to the junk folder (or reject the message) even before the message is received by the client anti-spam filter at all.


check  MailList Controller sends email messages in the same format as your email client.

check  The message encoding or the mailer itself is not the problem.

warning  In most cases the content of the message or the email account is the reason why a newsletter message gets detected as spam.

The Community:

Large mail provider like e.g. or are using sophisticated spam detection technologies, complex filter rules and most important: the community. Also many client based filters (plug-ins) include the community. If many recipients interact with your messages in a positive way by opening, reading or clicking on a link, then it's more likely that your message is not spam. On the other side, if most recipients mark your message as spam, there is a high chance that your message ends up in the junk folder.


warning  Send high quality content to your subscriber

warning  Personalize the message, e.g. use "Hello [Name]" instead of "Hello"

warning  Add an unsuscribe link to your newsletter - it's better as getting marked as spam

warning  Don't flood your subscriber's mail box with too many messages

warning  Make sure the message is still readable if images are blocked by the recipient's mail client

warning  Focus on the message (image) size - many people are using mobile devices to read their mails

Message Content and Subject:


warning  Do NOT try "dirty tricks" like useless filler text, misleading subject lines, misleading anchor texts, etc.

warning  Avoid typical spam terms like "business offer"

warning  Avoid excessive use of HTML code and don't use HTML5

warning  Avoid <div> and deeply nested tables

warning  Don't over-optimize your HTML code

warning  Don't use Javascript, Flash, embedded video, iframes, forms or external CSS code - it won't work at all, but could harm the spam rating

warning  Don't use tracking pixels or web bugs

warning  Avoid inline images with only a few words of text

warning  Avoid too many links in your mail

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List Email Address and Outgoing Mail Server (SMTP Server)


warning  Make sure the specified list email address belongs to the outgoing mail (SMTP) server!

This issue is very important - if the sender email is from a different provider, then you will be blocked by most anti-spam filters or the message will be rejected by the outgoing mail server.


warning  Use SSL (Port 465) or StartTLS (Port 587)

The mail header includes the route from the sender's client to the recipient's client.


warning  Use Sender Policy Framework (SPF) or Domain Keys Identified Mail (DKIM)

Today many mail server support the Sender Policy Framework (SPF), as defined in RFC 4408, or use the Domain Keys Identified Mail (DKIM) for associating a domain name to an email. SPF and DKIM are server based - it's not required to change or setup anything in MailList Controller.

"SPF is used to describe what mail server is allowed to send messages for a domain".
This means it's used to detect fake email addresses (as sender email address).
More Information about the Sender Policy Framework (SPF) by

"Domain Keys Identified Mail (DKIM) is a method for associating a domain name to an email, thereby allowing an organization to take responsibility for a message in a way that can be validated by a recipient." ... from
In other words (simplified): "Some organization (domain) has signed the message and is responsible for it".

Test your Message

It's recommended to send a few test messages to spam-protected email accounts and web mail accounts to verify the spam rating of the message.

Open the internal editor, click on "Test Email", enter your email address (in To) and send a test email.

Send out newsletters to subscribers only and allow them to unsubscribe! Adding an unsubscribe link is easy and takes only a few seconds.
See also: How to add an unsubscribe link to your newsletter

Test Message

Common Issues:

The header often contains details about the spam-rating:

1.1 MPART_ALT_DIFF BODY: HTML and text parts are different
Include a plain-text part to your HTML message. (use the "Extract ..." function)

Rename the inline image e.g. use 1.gif instead of header.gif

1.4 SARE_GIF_ATTACH FULL: Email has a inline gif
Use a different format e.g. PNG instead of the GIF image.

Replace the title tag in the html source code. (remove <title> ... </title>)

1.3 MISSING_SUBJECT Missing Subject: header
Add a subject to your message

1.7 SARE_GIF_STOX Inline Gif with little HTML
Add more text/html content or replace/remove image.

0.6 HTML_IMAGE_RATIO_02 BODY: HTML has a low ratio of text to image area
2.5 HTML_IMAGE_ONLY_16 BODY: HTML: images with 1200-1600 bytes of words

Add more text/html content or remove image.

1.6 MY_CID_AND_CLOSING SARE cid and closing
1.5 MY_CID_AND_STYLE SARE cid and style
1.6 MY_CID_ARIAL2_CLOSING SARE cid arial2 closing
1.6 MY_CID_ARIAL_STYLE SARE cid arial2 style

Remove style/font tags (<div>,</div>,<font>,</font>) before and after the <img ...> tag.
If its not possible ... try to change the font e.g. use MS Sans Serif instead of Arial.


See also: How to read and analyze the email header fields of a message