Originally Posted by scottmusician
Everyone else can send to the address OK.. and the email is coming from a user with a normal enough firstname.lastname@example.org
Contact the addressee and ask if they need to add your email address or your company email domain to a list of permitted email senders. Alternatively, your email domain might be on their company list of email domains to block.
Since others can send to the address, the address exists rather than what the error message is telling you.
However, the fact that you get the message says that the target mail server is not reporting that the address exists when YOUR messages are presented for delivery. In short, you knock on their door, but get "no one by that name lives here."
This sounds like a "white list" -- "black list" issue to me. (Others with more mail server admin knowledge might be able to say better or more accurately.) In short, something about YOUR message, as sender, is not acceptable to their servers. White and black lists are security measures to combat spam and other email based scum-ware attacks. These lists might affect only email, but might also affect access to web pages or other internet services.
- A white list is a set of email addresses or email domains, that the target server has been told to accept.
- A black list is a set of email addresses of email domains, that the target server has been told to deny.
For example, many corporate email servers black-list foreign countries and then white-list specific email domains for those foreign folks where they have legitimate business interactions.