Hi, i have a postfix server which is only used for sending emails to the outside, no incoming emails are allowed (no MX record). I recently opened port 587 in master.cf and now i'm asking myself if it is ok to close port 25 completely? AFAIK every mail server should accept incoming mails to postmaster@myserver, but when i close port 25 this is not the case anymore, isn't it?
and another question regarding port 25; when my postfix server generates a bounce message (which happens when sending a mail to non existend address) and sends it back to the originally envelope sender, he uses "From: [email protected]" as sender of the bounce message. Does [email protected] has to be an existend mail account? We recently had problems that on MX site of our email addresses (hosted by a company) they rejected some of the bounce mails generated by my server. Log shows following; "status=bounced (host mx.myEmailHostedByCompany.tld[IP.IP.IP.IP] said: 550 5.1.0 CfoC1j00P08HtnS01foCNg dominio non valido / invalid domain (in reply to MAIL FROM command))" So i'm asking myself does this error message mean that [email protected] has to be existend (so i have to keep port 25 open on my server and see if this account is ok)? Does myserver.tld need to have a MX record as well in order to avoid the problem? As far as i understand this error message means that the envelope sender (which is empty (<>) for bounce mails) is not valid, which is nonsense because every bounce message has an empty envelope sender. kind regards, Georg
