Contacts gem and mailing solution to handle email bounces

Hi,

My app has a feature to import contacts from gmail,yahoo and hotmail. I
am using CONTACTS gem to achieve that. The functionality is working
fine, I can import many contacts in bulk. I also have a “invite your
contacts” feature as well. Issue arises here: Quite a few of the invite
mails fail when we send the invitations to them. When this happens in
large scale ie many people inviting their friends using web import and
invite feature, bounces can go high in number. I am concerned about
rated as spam guys.

1.What is the solution to handle these bounces.

Not so important, but still wanted to seek suggestions for this :if
anybody is using such feature, how are you handling the queues of such
invite mails. if 100 people invite 100 others then we have, 10000 mails
already. Which itself will take 7-8 hours to handle. If the user base
grows then , time taken to handle the chunk will grow as well. Any
suggestions?