External domain users are not being imported - why ?

Hello,

In my farm , I have recreated UPSA for internal domain as well as for external domain.

Internal Users are being imported without any issue, while external domain users are unable to added into UPS.

UPS account is having replicate directory changes permission over external domain and trust connection has been set up and confirmed even though I am getting following errors for external domain connection during Full Profile Synchronization.

FIM ERROR:

Event Viewer Error:

Would you please help me to resolve this issue?

Thanks and Regards,

Dipti Chhatrapati