Postfix

For development, you don't want any e-mail sent to the outside world, but you do want to be able to see all mail your sites or application try to send. Here is a configuration of Postfix to do that.

The trick is to BCC everything to a local user, and discard without error any other sending.

This is based on several guides and Q&As online but well, none of them worked for me, so here's exactly what i did (minus all the missteps).

Status: we've enabled authentication, but can't connect to SMTP on port 25 with say an e-mail client to test the real way, and have a new error for testing on the server: 538 5.7.0 Encryption required for requested authentication mechanism

The main resource:
http://workaround.org/articles/ispmail-etch/#step-9-authenticated-smtp

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")

In short Agaric needs a robust e-mail solution for ourselves and our clients.

Debian Administration :: Handling mail for multiple virtual ...
http://www.debian-administration.org/articles/243

The immediately needed fix: