We are getting a very strange bounce off a valid email address, from a company who can send to other people on our domain. The person cannot send in to us and receives back this error:
"There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<messaging.asdf.com #5.5.0 smtp:550 permanent failure for one or more recipients (firstname.lastname@example.org:550 Requested action not taken: mailbox unavailable)>"
I have searched and searched to no avail, it just confuses me why it would happen on 1 person and they can send to other people within our company. Our Barracuda shows it Action: Allowed Delivery Status: Rejected (mail.vanderhaags.com:550 Requested action not taken: mailbox unavailable)... so it is going past the spam filter and being bounced on our Exchange 2010 server.