in the newly installed exchange 2019 I'm facing a problem, employees that send mails to outside with IMAP are getting this error in their inbox:
Server error: '550 5.7.54 SMTP; Unable to relay recipient in non-accepted domain'
the receive connector is the default connector and the domain that users are created is different than the email domain, here is the log I found the log
the xxxx.com is the real email address and YYYY.com is the local domain name
By default Exchange server won't let you relay emails to outside recipients.
You may need to follow these steps to create a dedicated receive connector used for relay:
1.create a new receive connector
It is not recommended by Microsoft to modify the default ones as it often causes issues.
2.configure the permissions on the receive connector
3.specify allowed ip addresses to allow anonymous relay only from these ip addresses.
If not, your server would become an open relay.
The detailed steps are introduced in this Microsoft documentation:
