Mail sent to recipients is returned undeliverable

Sending mail works fine except when addressed to anyone with a address. Anyone have a clue what the problem might be?  I’m using pop and smtp.

Thanks, Steve

Did you try sending a message from a web interface to that address? If it is working that way, try sending from eM Client again as it could just be an temporary issue.

But without seeing the actual return message, it is most likely that if your message is undeliverable, it means that either your server is not able to reach, or there is some issue with and it is not able to deliver the message to the mailbox.

Either way, eM Client is probably doing it’s job by uploading the message to your SMTP server. After that, you will need to contact the server admin from which the message originates to find a solution.

Thanks Gary.  Yes, I was able to send a message using protonmail so it must be a server issue.  Guess I’ll have to work it out with suddenlink or cox.