Postfix - Architecture (Processes)
postfix may starts several process, generally:
- one to receive and relay mail (port 25)
- one to submit mail (port 587)
Postfix services are implemented by daemon processes. These run in the background, started on-demand by the master(8) process.
- Check that the port is taken locally by the master postfix process
netstat -tulpn | egrep 'master|:25'
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 31278/master tcp6 0 0 :::25 :::* LISTEN 31278/master
See Postfix - Configuration (File, List and Default values)
There is a lot of configuration that you can see with their default value on this page.
- It needs to be open in order for it to receive mail from the internet.
- It should accept anonymous connections, but not for relaying
The process on port 25 is the default and is defined in the smtp line of the master.cf
# ========================================================================== # service type private unpriv chroot wakeup maxproc command + args # (yes) (yes) (yes) (never) (100) # ========================================================================== smtp inet n - n - - smtpd
It follows all configuration defined in the /etc/postfix/main.cf file.
- is considered a submission port. It is also what clients use to send mail out using your server.
- should only allow authenticated connections
See: The email submission port is where you connect to your email server to send an email