[CentOS] mail.centos.org : packets to strange ports

Reading a daily Logwatch report I noticed mail.centos.org sending packets to my outgoing mail server. The packets were blocked by IPtables.

From 72.26.200.202 - 18 packets

To xx.xx.xx.xx - 18 packets Service: 33120 (tcp/33120) - 2 packets Service: 33906 (tcp/33906) - 4 packets Service: 39856 (tcp/39856) - 2 packets Service: 42049 (tcp/42049) - 2 packets Service: 54517 (tcp/54517) - 2 packets Service: 54792 (tcp/54792) - 4 packets Service: 58445 (tcp/58445) - 2 packets

I thought all outgoing mail dialogue was conducted on port 25. Incoming mail from Centos is usually received by a different server.

Thanks,

Paul.