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Old 15th March 2011, 03:03
carlosinfl carlosinfl is offline
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Location: Orlando, FL
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Default Sending Mail Via Telnet?

So I got a mail server stood up running Postfix running it's most simplistic configuration for a single domain. I created the shell users in Debian & set their home directory as their mailbox.

My question is after I added about 40 users, I realized that anyone can simply Telnet to my mail server on port 25 and compose a message and say they're someone else:

telnet my.mailserver.tld 25
EHLO mypc.mydomain.tld
MAILFROM: bob@mydomain.tld
RCPTTO: theboss@mydomain.tld

Hey! You're a fat pig & I quit!
Message queued as S7439OP32
So I can send that from any PC on the domain and claim that I'm 'Bob' when in fact I'm not. This seems like a really big issue for security & authenticity for Postfix / MTA. How can I resolve this issue and or prevent it from happening?
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