Forum Discussion
hybrid user not able to send to single office365 mailbox
i have hybrid onprem user mailbox who not able to sent only one office365 mailbox user, that on prem mailbox user able to send rest of office365 mailbox user.
I am getting error Remote Server returned '< #5.4.4 smtp;554 5.4.4 SMTPSEND.DNS.NonExistentDomain; nonexistent domain>' and msg tracking
2 Replies
Please verify your DNS setup, internal DNS as well
https://learn.microsoft.com/en-us/exchange/mail-flow-best-practices/troubleshoot-mail-flow?source=recommendations
Please check this documentation.
