Invalid Status For Recepient- Message XS899- Emails Not Releasing

Hi All

I have configured emails in one of our clients. I have included all possible steps for it but still emails are failing.

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a) The user sending emails has already email mentioned in user master at SU01.

b) The mail host is reachable & is successfully completing.

c) Routing test is successful through SCOT.

Regards

Pankaj