Sendmail relay through ssh tunnel?

[federico]

Hello, Is it possible to setup sendmail to relay all smtp mail through an
ssh tunnel?  

I am in a network that restricts all outgoing mail traffic to single
exchange server host, so everyone has to use the exchange server to send
emails.  

On a windows computer I can setup the ssh tunnel and then point my email
client to localhost, but, if at all possible, I would like to setup
freebsd box as an smpt server that other hosts can use.

Any pointers will be greatly appreciated.

federico