Self-signed certificates in Mail.app
I run my own mail server, including an IMAP server. I use SSL, but I was not about to pay Verisign (or anyone else) for a signed certificate. I had been putting up with the “trust this certificate?” messages every time I started the Apple Mail.app, until I came across this Apple support article.
It describes how to import your self-signed certificate into your key chain, so Mail doesn’t bother you any more.