Couple of Questions about SSPR

Good day, 

I don't have much experience with SSPR and I thought that this would be the place to start asking a few questions for my customer.

Customer is experiencing mail not being accepted by SMTP servers and it is aging out of the queue. They have changed the value to 10 hours but they are still seeing the issue happening. 

They mentioned using the appliance for SSPR, where would the mail queue be located on the appliance? 

The mail appears to open a single session dumping multiple emails using that session, customer is asking if it can be configured for 1 session per email or is there another method of configuring mail that would alleviate some of the backlog that the customer is seeing/experiencing?

I can try to provide more information if requested and again I haven't used this in much detail depth so not really sure where to start looking to help them. 

Thank you, and have a nice day ahead.