I've installed dovecot, postfix and roundcube on an ubuntu 12.04 box. The system is basically working - i.e it is able to send/receive mails to/from other domains.
However, some domains cause the following error message in /var/log/mail.log
Jul 15 01:59:21 one postfix/smtp[2019]: 0D0399C025F: to=<someone@destdomain.com>,
relay=sm01.destdomain.com[x.x.x.x]:25, delay=0.56, delays=0.4/0/0.06/0.1,
dsn=5.5.2, status=bounced (host sm01.destdomain.com[x.x.x.x] said:
504 5.5.2 <contact@localhost>: Sender address rejected: need
fully-qualified address (in reply to RCPT TO command))
Do you have any idea what's wrong here? I.e. How to force postfix to use "contact@mydomain.com" instead of "contact@localhost" when connecting to another mail server?
Any hints are appreciated.