What is the function of the SSL Cert in Exch 2010

[pinytech]

I have read that to encrypt outbound email messages we can configure/use SMIME or some other 3rd party method.
But this leaves me a bit unclear as to what exactly Exchange 2010 uses the SSL Cert for???
I've read things like:
1)Internal client-server communication is encrypted - is this true? is it in-transit only?
2)the sesssion is encrypted. - That's nice but doesn't a session include transfer of SMTP messages?
I hope someone can shed some light as to what exactly our SSL Cert is doing for us in our not very complicated environment.
Thank you all

 

[DrB0b]

You may want to give this a read:

https://practical365.com/exchange-server/exchange-2010-ssl-certificates/

Learning - A never ending quest for knowledge usually attained by being thrown in a situation and told to fix it NOW.