Seems that the problem (for me) was that it didn't trust the certificate authority that signed my certs, which is StartCom SSL. There's a bug in Android's bug tracker to support this CA (Microsoft, Apple, Mozilla, and more already do) and it looks like it might happen in 2.2, although I'm not entirely sure.
What I did was install k9mail, which prompts you and allows you to accept untrusted certs. This is a much better solution anyways because it supports using your online Drafts/Sent/Trash folders instead of storing everything sent into local folders. k9mail is open source and is in fact a fork of the original Android mail client.
You can find it here:
k9mail - Project Hosting on Google Code