I am getting the following returned mail whenever i send to a certain address:
------ Failed Recipients ------
<firstname.lastname@example.org>: Requested action not taken: mailbox unavailable. [SMTP Error Code 550]
THe interesing thing is I hit reply on an email sent from this address.
I understand that this meand the mailbox is unavailable.
What are the possible reasons this could occur?
How can I trouble shoot this?