Odd qmail Problem: Mail delivery from certain senders takes up to 10 hours

[DReffects]

Hey Guys,

I am running CentOS 5.10 (Final) with Plesk 11.5.30 Update #44 and since a few days have the strangest problem with incoming emails from certain hosts.

The email from known senders produces a relaylock message like:
/var/qmail/bin/relaylock [12345]: mail from 80.80.80.80:59595 (mail.hostname.com)

From what I was able to gather this is regular behaviour with plesk and qmail, indicating that the senders' mailserver has made contact.

Then nothing happens. For hours. 7-10 to be exact. Then the mail is being processed and delivered.

Any Ideas how to troubleshoot this?

Thanks

 

[InderS]

Hello,

May be there is a lot of mails are stuck in your server mail queue and due to that your server is taking time. Check your mail queue and delete all old mails from server mail queue.

 

[DReffects]

Hello,

May be there is a lot of mails are stuck in your server mail queue and due to that your server is taking time. Check your mail queue and delete all old mails from server mail queue.

Well no, that's what makes it so strange: while these specific mails are 'stuck' other mails I send to the same mailbox are getting delivered instantly. Nothing in the queue.