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WordPress Spam Filters – How Akismet Determines Comment Spam


Comment spam can become a huge problem for blog owners. But the systems that safeguard against comment spam can become your worst enemy if you find yourself being unfairly labeled as spam.

Currently, there are three legitimate bloggers that almost always end up in my Akismet spam filter on, and I’m sure that there are many more out there along with businesses who are using good commenting practices to build traffic and links to their websites. So this post is for all valuable commenters who have, for one reason or the other, been placed in the sandbox known as the spam filter.

What is Akismet?

Akismet is a system for WordPress blogs that checks incoming comments and trackbacks against a database to determine if the item is legitimate or spam. For self-hosted blogs built on the WordPress platform, it is a plugin that must be activated by the blog owner, and for blogs hosted on WordPress.com, it is automatically built in.

Awaiting Moderation or Akismet Spam Folder

How do you know if your comment has been shoved to the Akismet spam folder as opposed to simply sitting in the moderation area? There are a few telltale signs that I have come across, including the following.

Possible Akismet Flags

So how does the Akismet database determine if your comment is legit or spam? Items in the Akismet database are submitted by blog owners through their comment moderation dashboard. If a blog owner considers a comment spam, they can mark that comment as spam which adds the commenters’ details to the Akismet database.

The following are details of the comment analyzed by the Akismet system, as listed in the Akismet API, plus some observations on how they affect comments. Keep in mind when reading these that it is not always one particular comment detail that Akismet analyzes to determine if the comment is spam – it is a combination of details.

IP Address
The IP address of a commenter is always logged. If spam comments get past the Akismet check, blog owners can view the IP address of each comment, which can lead to comments from the same IP with multiple names and details being marked as spam.

If one comment from your IP address is flagged as spam, are all comments using the same IP going to be filtered? Not necessarily. The IP address in combination with the next comment details will determine if comments are sent to the spam or moderation folder.

Comment Type
Akismet monitors not only regular comments, but trackbacks and pingbacks as well. For some blogs, trackback spam is much worse than actual comment spam.

Comment Author
The name submitted with a comment can be a major trigger. For example, using a keyword phrase in the name field that has been often marked as spam, such as Viagra, can automatically send a comment to the spam filter. Sometimes, if you receive one of the signals that your comment has went to the spam bin, you can simply hit the back button, change your name (try something real like your actual name or Bob if you’re shy), and the same comment will go into moderation instead.

Comment Email Address
Email addresses seem to be a particularly sensitive trigger for Akismet, particularly freebie emails such as Hotmail, Yahoo, Gmail, Inbox, etc that spammers use frequently. Using an alternative address, perhaps from your own domain, may help bypass the Akismet. Of course, if you are spamming the comments section and getting reported under your domain’s email, then you may end up adding your own domain to the Akismet filters.

Comment Author URL
This is the URL you enter in the website field of the comment form. If a particular URL is marked often as spam, that URL field will trigger Akismet to bounce the comment into the spam folder. This determination is sometimes in conjunction with the email address, author name, and IP – changing these other variables could help the comment URL go through.

Comment Content
The actual body of your comment if analyzed. Common phrases such as “great post” or specific keywords may get a comment labeled as spam. Also, like the URL field itself, if the comment content contains links to a domain that has been reported as spam, the comment could get flagged as spam. So simply removing the URL from the website field and placing an HTML link in the comment content may not help a comment bypass Akismet.

What You Can Do

So what should you do if you feel like you are being unfairly marked as spam? As a commenter, you can try changing some of the above comment details such as commenting from a different computer, leaving out the keywords in your name, or using a custom domain email address.

To get the attention of a blog owner where you feel your comments are not being approved, simply try their contact form and let them know you have recently left a good comment on their post but think it may have been filtered into their spam folder. Also, make sure to have a Gravatar – a personal image definitely helps your comment stand out to blog owners who do review their spam filter often.

In the long run, remember that the more times blog owners mark your comment as not spam, the better your chances of getting out of the Akismet auto filter. Every valuable comment counts!


Update 6-7-2010: Depending on your perspective, a huge flaw in the Akismet system has been recently discovered. Akismet is deleting certain comments without sending them to your spam filter, which means there are comments coming to your blog that you will never see. Read more about how Akismet is deleting comments.

Your Thoughts

Are you a good commenter who commonly who suspects you are being caught in the Akismet spam filter? What have you tried to get yourself out of it in terms of changing your details or contacting blog owners?

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