Remote Server returned '550 5.7.129 RESOLVER.RST.RestrictedToRecipientsPermission

enduser2021 · Post by **enduser2021** » Mon Nov 08, 2021 10:10 pm

Client appears to be using O365. We are using Zimbra.

Client has reported this error when sending an email to one of our employees:

Diagnostic information for administrators:

Generating server: ********.com

*****@*******.com
Remote Server returned '550 5.7.129 RESOLVER.RST.RestrictedToRecipientsPermission; not authorized to send to recipient because the sender isn't on the recipient's list of senders to accept mail from'

How can this be when we do not use O365 and we have no such option to accept or deny senders?