Postfix on Debian: Fixing the bounced email issue "553 5.5.4 ... Domain name required for sender address root (in reply to RCPT TO command))"

After many google searches, Pickcoder on the Freenode IRC channel #postfix helped me out with this one.

After setting up Postfix as the MTA on a Debian box using these instructions, I was able to send email through the SMTP server. However, when sending from the command line, I was getting bounce messages in my /var/log/mail.info file:

shell$ mail -s "Test email" someone@somewhere.com
this is a test [ctrl][d]

shell$ tail /var/log/mail.info
Jul 16 13:17:44 server postfix/smtp[873]: E676D180278: to=, relay=email.somewhere.com[12.12.123.123]:25, delay=0.63, delays=0.05/0.02/0.44/0.11, dsn=5.5.4, status=bounced (host email.somewhere.com[12.12.123.123] said: 553 5.5.4 ... Domain name required for sender address root (in reply to RCPT TO command))

The trick to fixing this was that the account (root in this example) didn't get its hostname nor FQDN attached to the end of the address, so my email looked like it was coming from 'root' rather than 'root@someserver.com'.

The actual fix is to edit the /etc/postfix/main.cf file and chage the line that reads "append_at_myorigin = no" to "append_at_myorigin = yes"

Edit the file with vim or your preferred editor:

shell$ vim /etc/postfix/main.cf

and change the line from

append_at_myorigin = no

to

append_at_myorigin = yes

Make sure to restart Postfix:

shell$ /etc/init.d/postfix restart

And then try your mail command (up above) again. If you check the mail.info logfile, the status should now read, "status=sent"