Not sure if this is due to security; hence the reason i am asking here. I have 2 SMTP server and a couple of unix servers
- the actual mailserver running on window. client connect to it and download mail.
- a postfix SMTP server running in one of the unix box use for relaying mail to 1).
We call my mailserver MTA1 and the POSTFIX server MTA2
I am a novice in mail and i realize these following different flows when some of the different unix servers are sending mail to the public
They can either
unix server (mailx) --> (localhost-sendmail) ---> MTA2(postfix) --> MTA1 (actual mailserver) --> external MTA
unix server (mailx) --> MTA2(postfix) --> MTA1 (actual mailserver) --> external MTA
unix server (mailx) --> MTA2(postfix) --> external recipient MTA
unix server (mailx) --> MTA1 --> external recipient MTA
unix server (mailx) ---> (localhost-sendmail) --> external recipient MTA directly ?
q1) Is all the above paths valid ? If so, what should be the correct way ?
q1) Notice 1), not sure why there is a sendmail listening on localhost when the MUA can go directly to MTA2 or MTA1 (like path2)
q2) Notice 2) not sure why the need for MTA2 to relay to MTA1 when they can go the 3) path
q3) Notice 3) not sure why the need to go to MTA2 when they can go to MTA1 also
q4) Notice 5) i have a strong feeling i can send to the sendmail on localhost and have it send to the external MTA directly.
So which is the right path ?