Debian server not sending mail to recipients that share its domain name

In Agaric's case for this server, mail for the domain was in fact being handled elsewhere. The problem was the server thought it should do it, so it caught all the mail with its domain name and squashed it, saying "there's no user by this name."

Jan 8 11:01:31 stedile postfix/local[28262]: A35D064CFD: to=<Herrera@example.net>, orig_to=, relay=local, delay=0.12, delays=0.05/0.01/0/0.06, dsn=5.1.1, status=bounced (unknown user: "herrera")

Jan 6 13:07:41 stedile postfix/local[22758]: 3419664CA2: to=support@example.net, relay=local, delay=0.03, delays=0.01/0.01/0/0.01, dsn=5.1.1, status=bounced (unknown user: "support")

List all the domains you wish to handle mail for, in the file /etc/postfix/virtual/domains.

Thanks to the ever-amazing
http://workaround.org/articles/ispmail-etch/#local-domain

I figured out where to look

a search for example:
/example
And there it was:

mydestination = example.net, stedile, localhost.localdomain, localhost

xxxxx... to get rid of example.net

mydestination = stedile, localhost.localdomain, localhost

and shift-ZZ to save and get out of there

And to reload the main.cf configuration:

postfix reload

should be good now.

Jan 10 10:34:46 stedile postfix/postfix-script: refreshing the Postfix mail system
Jan 10 10:34:46 stedile postfix/master[1618]: reload configuration /etc/postfix
Jan 10 10:34:47 stedile postfix/qmgr[10249]: E194C64CC7: from=support@example.net, size=898, nrcpt=1 (queue active)

And the e-mail came through! Yay!

Resolution

Remove your domain from the mydestination string in Postfix's main.cf.