Weird E-Mail Issue

Recently, myself and some of my clients have been recieving e-mails that seem to be originating from Interworx…

The e-mails come 1-3 at a time, completely randomly from domain.com@server.sliqua.com (replacing domain.com with their account domain) and end up in their inboxes.

Any ideas?

Sliqua,

What the content and header of the e-mails?