emails being rejected

[sime]

Hello

I am losing every second email from a listserver to email addresses on my cpanel managed server.

Ie.
client@unrelateddomain.com receives them everyday.
client@cpaneldomain.com receives only every second day.

I've reproduced the problem with my own email addresses.

I'm here because there is something weird about the failing emails. Here is a comparison one of the "Received From" lines in headers (linefeeds added):

This from a header that succeeds to both addresses:

from unknown (HELO mail-ihug.icp-qv1-irony2.iinet.net.au) ([203.59.1.196])
(envelope-sender <owner-SOME-LIST@LISTSERV.AOL.COM>)
by mail.iinet.net.au (qmail-ldap-1.03) with SMTP
for <myaddress@ozemail.com.au>; 8 Jan 2007 05:14:33 -0000

This from a header that fails to one address:

from unknown (HELO customer-domains.icp-qv1-irony14.iinet.net.au) ([203.59.1.169])
(envelope-sender <owner-SOME-LIST?myaddress??OZEMAIL?-COM?-AU@listserv.aol.com>)
by mail.iinet.net.au (qmail-ldap-1.03) with SMTP
for <myaddress@ozemail.com.au>; 9 Jan 2007 05:01:36 -0000

Can anyone provide any advice? It is mighty strange to me that an automated list-server (mailman?) digest should have difference headers.

Needless to say, both the list owner and my hosting company both deny any problem on their end. And because I'm on a shared server with cpanel and i can't review the logs myself. My next step would be to move my customer to my VPS -- but if this fixed the problem I would then not know if other addresses on my shared server are compromised.

Thanks for any input.
Simon

[sime]

Whatever I've been seeing in the headers has not been causing the problem. I'm not seeking a solution to my OP anymore. Thanks