I do not from whence (I see no client connection from /var/log/mail.log) the
weird letters come, but I see them as:
postfix/qmgr: 4B59323B3A: from=<>, size=3751, nrcpt=1 (queue active)
latter then they are sent:
postfix/smtp: 4B59323B3A: to=< ... at yyyy dot zz>, relay=none, delay=147396, delays=147365/0.07/31/0, dsn=4.4.1, status=deferred (connect to yyyy.zz[aaa.bbb.ccc.dd]:25: Connection timed out)
So, can You please help me with the following, how I can:
- investigate (debug?) from whence it comes? and
- filter/ban it?
Thank You for Your time.