postmaster domain

[Timothy Murphy]

I recently upgraded a remote server to CentOS-7.2,
after which email stopped coming through.
I suspect that this was probably due to the fact
that I had started a version of dovecot installed some time ago.
I found messages in /var/log/maillog like
  Jan  4 12:56:56 alfred postfix/lmtp[7612]: 20A662202B4:
    to=<root at gayleard.eu>, relay=alfred.gayleard.eu[private/dovecot-lmtp],
    delay=34272, delays=34272/0.16/0.01/0.05, dsn=4.3.0, status=deferred 
    (host alfred.gayleard.eu[private/dovecot-lmtp] said:
    451 4.3.0 <root at gayleard.eu> Invalid user settings.
    Refer to server log for more information. (in reply to RCPT TO command))
Googling for this, I found the suggestion that one should insert
the following postmaster_address line in /etc/dovecot/conf.d/20-lmtp
  protocol lmtp {
    postmaster_address = postmaster at alfred.eu
    # Space separated list of plugins to load (default is global ail_plugins).
    mail_plugins = $mail_plugins sieve
  }
(alfred.eu being the server's domain).
This seems to have solved the problem, after re-starting dovecot.

I'm wondering if this was an issue that arose some time ago,
and if so whether my solution was the recommended one?

-- 
Timothy Murphy  
gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin