Slow Sending - Ticket email info table?

Hello,

I have a (hopefully) easy question.

Every time I would send an email out via the ticket system, it would try to write to ticket_email_info with the following query:
SELECT email_mid, headers FROM ost_ticket_email_info WHERE thread_id=787119 (random)

This query would take forever and run multiple times, slowing down the sending a ton.  Ticket_email_info is huge, hundreds of thousands of entries.  I went in and truncated ticket_email_info, and it seems to have solved the problem without causing any issues in the system. 
My question is what does ticket_email_info do?  Is it OK to delete it like that?  It looks like it's storing email header info, but I can't figure out why.

I'm happy to attach my config info, but this is a more general question.

Thanks!