Group bcc: which email is undeliverable?

  • Answered
I sent group emails out to a team. Some of the emails are returned for various reasons. How do I find out which recipient is being returned? Below is a sample of a returned message. I am using Outlook for Mac version 15.18. I am unable to find any other detail.

[Return Code 550] sid: 7uSM1s0043ZCSgq01 :: 5.1.1 Not our Customer
[Return Code 521] sid: 7uSM1s0043ZCSgq01 :: 5.2.1 : (CON:B1)
[Return Code 550] sid: 7uSM1s0043ZCSgq01 :: Access denied...34f598a125a161f5f87de9e9b17d7d65fc082d08bd58b94cbd4c6d014149014c49410c49f939...

Thank you.
Hello CS, Thank you for contacting us about undeliverable mail. The Return Code 550 -- Not our Customer -- typically means the address was unreachable either because it is no longer present on the server, or was typed incorrectly -- basically not able to be found. The Return Code 521 -- ( -- indicates that AOL did not trust the connection because of possible spam. I advise going through your mailing list to make sure those email addresses are up to date. I also recommend using a dedicated email marketing application like phpList. Best, Christopher M.