My company's email is hosted through http://everyone.net but we host our own DNS.
The mail server host is
We've been using this email all setup for a few years but recently I've had a couple people from different companies (both are hosted through a hosting provider Cogeco though) report that they can't send to us.
The following recipient(s) cannot be reached:
firstname.lastname@example.org on 15/10/2010 2:34 PM
The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator.
< fipsb03.cogeco.net #5.0.0 smtp; 5.4.7 - Delivery expired (message too old) [HotMail_Bounce] 450-'Recipient Rejected: Too many unknown recipients, please clean up your list' (delivery attempts: 10)>
Does anyone know what I can do to find out what's wrong?