I'm using Stunnel because I use Eudora and check several gmail accounts (along with non-gmail ones). Gmail changes their SSL certificates about every two weeks. Eudora, being old, doesn't handle SSL certs well so each time Google changes them, you have to go to each gmail account settings and approve the new certificate. It's a PITA. So by using Stunnel on those accounts it handles it and saves a bi-weekly series of certificate approvals.
It's what I get for liking an old outdated email client!