Hi Midhun,
After trying all the possible options, I have raise the OSS massage and in response I came to know that it was a bug in the current release (SMP 2.3.4.281). which was later fix in SMP 2.3 SP04 (with latest patch - 2.3.4.335)
with the latest patch i simply map the outbound enabler with certificate and it started working for me.
Kind Regards,
Amey