A word of warning: if your email server requires SSL, expect problems.
I had my fair share thanks to self-signed certificates (Exchange Server and an IMAP server of unknown pedigree), and for other unexplained certificate problems (a Lotus Domino, with a certificate that appears to be valid and trusted all the way up).
Needless to say, an iPhone will just ask you (once!) if you want to accept the certificate, install it and just work. With a WP7 you have to get hold of the actual certificate, email it to the device, install it from the attachment, reboot the phone.
And since self-signed certificates expire every year, you never run out of fun...