TLS handshake error in mail

I've been getting a number of complaints about missing mail coming in to our
server. The errors these folks have been getting is (reason: 403 4.7.0 TLS
handshake failed.) The messages try for a time and finally fall out of the
Mail Server's Queue. Any ideas?

Duplicate post.

Identical post has been answered and moved to "Networking, Security & Administration/Other" forum.

This thread is now locked.