This is an error from the command "tail -n 100 /usr/local/psa/var/log/maillog"
Aug 12 10:39:16 server1 postfix/smtp[4256]: F400424C1D: to=<
[email protected]>, relay=none, delay=298593, delays=298593/0.09/0/0, dsn=4.4.3, status=deferred (Host or domain name not found. Name service error...