Messages stuck in inbound queue and the following error is logged:
Feb 17 02:45:29 mail postfix/smtpd: warning: connect to 127.0.0.1:2501: Connection refused
Feb 17 02:45:29 mail postfix/smtpd: warning: problem talking to server 127.0.0.1:2501: Connection refused
Greylisting daemon is listening on tcp socket 2501 and this error means the greylisting service is not working. A restart does not helps. The problem is with a corrupted Libra Esva database, so please repair your database and everything will be back online.
You can proceed as described here.