Email NDR - How can I Find The Problem

[ElijahBaley]

I have been receiving quite a lot of Bounce back NDR's recently - how can I establish where the problem is
My ISP or the recipients ISP

Sometimes a mail will be gone for days until finally we will receive a NDR - the intended recipient will insist that they have been receiving there mail as normal from everyone else.

Are there some tests that I can do to work this out?

Thanks for your comments

Graham
"r tape loading error"

 

[Guest_imported]

What error message do you get on the returned emails?