I have to move one of our partners domain from our exchange server to another mail hosting provider. The migration of the domain to the mail provider was fine. They are able to send and receive emails normally.
After this I removed the accepted domain from our exchange server. The following steps were taken.
1. Backup of the mailboxes
2. Remove mailboxes
3. Remove mail policy
4. Remove the accepted domain
5. Remove DNS from the network.
6. Updated the off-line address book
But still unable to send the domain now hosted outside our exchange. Getting the following error.
#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##
Any assistance will be highly appreciated.