How to find who sends spam from the server?

Question

Email

There is a server on Debian with postfix, which runs several sites. I constantly end up on spam lists due to the fact that someone sends mail from my IP. For about a month I've been trying to find who and what, but to no avail. These addresses are not in mail.log. These addresses are not in the PHP mail send logs. I can not understand how you can send a letter and not get into the log?
Passed all sorts of tests for open relay, etc. - all closed. Special services do not show any errors, even DMARC prescribed that it should not be considered an error.
junkemailfilter.com sends a sample email - it's obviously spam. For example [email protected] to [email protected] with the subject Do you wanna meet and get laid or not? and corresponding to the content with the spam link.
Tell me who is in the subject - how else can I find the sender or method of departure?

Answer 1

It is quite possible that some left script is running on the server that directly sends letters via SMTP. In this case, there will be no entries in the logs.