SMTP, Contact form & going back in time.

Hey there,

Wondering if anyone else has run into this particular situation. My host changed their settings in php.ini (i think) and our site contact form wasn't sending emails out. I installed the SMTP module, and all is running smoothly again, but I have two questions:

1. What are the lines in php.ini that I would look for to find out if this is for sure the reason that Drupal stopped sending mail?

2. Is there someplace that all the mail that was sent that never went through is stored? I need to go back in time if possible and find all the messages that we've missed over the last couple of months. I am not sure if I need to ask my host for this, or if there's some sort of queue where messages go that get stuck. I am worried there is no answer to this because Drupal tells a user that their email is sent, and there are no errors in Drupal's logs.

Thanks for any advice you have on these issues.
mosa