Server attack while sending emails with link

Question

I have a problem with a web server, that also sends newsletter emails with an unsubscribe link. Everytime such an email is sent out, the unsubscribe link is called directly. Because it could be 1000 or more email, the calls crashes the server everytime. All emails are directly sent to Trend Micro Hosted Email Security. First I thought, there is malware on the machine, but checking for that gave no result. I now changed the machine, but it happens also with a completly new machine. The ip addresses of that calls are all from Amazon Webservices. I blocked a lot of this ip ranges already, but that is no góod solution.

What kind of server attack is that? What can I do, to stop or at least handle it?

I'll appreciate your hints.

Thanks

Vera

Answer 1

This looks like your emails are all going through some sort of email security scanning service, either on your servers, or on the recipient's servers. Typically, these scanners will also scan any links present in emails to ensure they are not malicious. There is no great solution to this. If you are scanning all your outgoing emails, you disable that, which may or may not be a good idea. See also Strategies to prevent email scanners from activating "unsubscribe" links .