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By Matthieu, 2015-12-09 10:40

When setting up Postfix on Ubuntu/Debian as “Internet Site with smarthost” to use an external smtp relay, automatic e-mails intended for “root” (such as cron job error reports) get sent out to the smarthost with a To: address of [email protected]. This can cause a problem as the smarthost doesn’t know where to deliver these messages to, since myhost.mydomain.com has no MX record.

The fix for this is (go figure) in the Postfix README:

Delivering some but not all accounts locally

A drawback of sending mail as “[email protected]” (instead of “[email protected]”) is that mail for “root” and other system accounts is also sent to the central mailhost. In order to deliver such accounts locally, you can set up virtual aliases as follows:

1 /etc/postfix/main.cf:
2     virtual_alias_maps = hash:/etc/postfix/virtual
3 
4 /etc/postfix/virtual:
5     root     root@localhost
6     . . .

Translation:

• Line 5: As described in the virtual(5) manual page, the bare name “root” matches “root@site” when “site” is equal to $myorigin, when “site” is listed in $mydestination, or when it matches $inet_interfaces or $proxy_interfaces.

Execute the command “postmap /etc/postfix/virtual” after editing the file.

Oddly, just adding the line

root: root@localhost

to /etc/aliases doesn’t work. You really need to do the steps outlined in the manual.