The following non-delivery report:

A problem occurred during the delivery of this message to this email address. Try sending this message again. If the problem continues, please contact your helpdesk.
A problem occurred

means that the recipient mail system did not accept the message either beacuse of a temporary issue on any party's end or because the recipient email address was not found in the recipient system.

The Diagnostic information for administrators section may contain the following errors:

#5.0.0 smtp; 500 Invalid recipient (#5.1.1)
Invalid recipient

#5.0.0 smtp; 500 No such user here
No such user here

Both these errors are usually generated in cases of external delivery (from Smarsh Hosted Services mailbox to an external recipient). They indicate that either the spelling is wrong or the recipient mailbox no longer exist. You can check if that is the case by:

#4.0.0 smtp; ESMTP not accepting connections
ESMTP not accepting connecitonsThe error is usually generated when the sender's IP address is blacklisted. While it is the sender's responsibility to ensure their IP address doesn't get blacklisted, you can contact Support for IP address removal evaluation.

If the IP address, however, is blacklisted on other public blacklists, contact the sender so that they could request delisting.

#554 5.7.1 Service unavailable; Client host blocked

554

The error is usually generated when the sender's IP address is blacklisted on invaluementSIP. To delist the IP address from ivaluementSIP blacklist you can request the delisting from https://www.invaluement.com/removal/

Note: since Smarsh Hosted Services is not the owner of the sender's IP address, we can only work with our spam-filtering vendors and not any other blacklists.