Click thru links are the hyperlinks that you might include in an outbound email campaign to enable you to monitor the effectiveness of your email marketing.

Some well know spam filters will automatically trigger click thrus without the recipient clicking the link. How does this happen?

To appreciate what is happening in this situation, you need to understand a little about how spam filters often work, including some of the better known products on the market.

A spam filter will need to 'follow' the links in an email to determine if the email is legitimate or if the content falls within its scoring rules. In short, it follows the link to see what is on the other end and check if it is malicious.

Yes - this means that if the spam filter sees a link in an email, it will follow the link to ascertain if the landing site is reputable or relevant. This often registers the same results as the recipient clicking the link themselves in the email.

This regularly happens before the email has arrived in your Inbox.

Is there anything I can do?

Sadly, because this behaviour is controlled by the spam filter your recipient is using, you can do very little to stop it.

This problem has less to do with the actual content of your email, but with the process of checking for spam that is being applied to all inbound emails to your recipient - in other words, it's not personal.

Update: We have seen this behaviour more over the last few months. This increase is probably because of updates to some of the larger online filtering products - this is now documented as a potential issue with a number of the bulk emailing platform providers. For further information, these links may be helpful;

Mailchimp article:

This quote might help, taken directly from Mailchimp - arguably the best known email marketing platform.

"My open rates seem high.

Here are some common issues that can cause your open rates to be too high.

A spam filter is causing high open rates. 

Aggressive spam filters will click links in incoming mail before delivering them to make sure there isn't any malicious content. Our system automatically tracks clicks as opens, and we have no way of differentiating when a click is from a spam filter. This can sometimes lead to an unusually high number of opens from a single domain. If you notice this on your report, it's likely the result of a spam filter. We recommend you ask your subscribers to whitelist MailChimp’s servers."

Barracuda : - this very popular online scan and filter service is known to follow links in emails as part of its mail assessment process - this does auto trigger click thrus.

Microsoft M365 : Microsofts built-in spam and malware protection will follow links to confirm they are not malicious. This will often result in a click being recorded.

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