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Spam emails using my mail server

Posted: Mon Aug 19, 2019 1:27 pm
by marcosmezapy
Hi,

My mail server is allowing passing external domains using my mail server to my local users.

Example:

Mail server: mail.mydomain.com
From: fake@anotherdomain.com
To: user@mydomain.com

This is possible through telnet shipments (port 25)

Achieved that my users have to register in a mandatory way to send emails:

If the following is done:

Mail server: mail.mydomain.com
From: fake@mydomain.com
To: user@mydomain.com

and do not log in, it will be rejected.

But I don't have control over other domains that want to use my mail server and this generates spam.

Could you help me?

Thank you!


I'm using Zimbra 8.6

Re: Spam emails using my mail server

Posted: Mon Aug 19, 2019 2:36 pm
by phoenix
marcosmezapy wrote:Hi,

My mail server is allowing passing external domains using my mail server to my local users.

Example:

Mail server: mail.mydomain.com
From: fake@anotherdomain.com
To: user@mydomain.com

This is possible through telnet shipments (port 25)
That is perfectly normal and how a mail server works. What ZCS does not do is relay emails through your server into the internet, that's called an open relay and by default ZCS is not configured to do that unless you've modified it. The other possibility is that your server has been hacked.

You're using a remarkable old version of ZCS and you should be on the most recent 8.8.15, there are security problems with earlier version of ZCS.

I'd suggest you look at the Administrators forum and read the first thread about a CVE that's exploiting ZCS server and see if your server has been hacked.