Use secure protocols. I have SSL with a CA-signed cert (and the CA cert installed) for IMAP, SMTP and WWW, and I use GSSAPI to authenticate myself to the IMAP and SMTP servers. I use ssh with a primed set of host keys, and GSSAPI.

Hardwiring is only useful if you never let anyone untrustworthy in. Just assume the medium is insecure to start with.