Email bounce back 550 5.1.1 recipient rejected
- by Stan
A client recently switched to Exchange Server / Outlook for their email. Since then emails from my company to any email address at their company bounce back from the System Administrator with this error:
  Your message did not reach some or all of the intended recipients.
   Subject:  Email Solution
   Sent: 12/12/2012 11:08 AM
   The following recipient(s) cannot be reached:
   '[email protected]' on 12/12/2012 11:08 AM
    550 5.1.1 <[email protected]> recipient rejected
Looking in the Message Options of the bounce back email shows no data in the Internet Header field. 
My client's IT guy says we're not being blocked, but I cant think of any other reason the bounce would occur. 
Any suggestions on what questions to ask or how to fix this would be helpful. 
I'm using a desktop version of Outlook 2007 and connecting through my ISP.
Thanks.