This was originally written for a slightly different context, and has been converted to serve as a krusty oriented tutorial. Please let me know of any errors or typos.
Krusty has OpenSSH installed already, so you just need SecureCRT, from Van Dyke (http://www.vandyke.com/).
Version 3.0 is slightly older, but the method is probably similar in newer ones.
Bring up the properties window for the server session where you want to tunnel. For Krusty, this is the session for setting up a secure connection to krusty-motorsports.com. You'll see the connection info that you've got set up (By the way, make sure that you're using ssh2 as your protocol; ssh1 has some security weaknesses. I also suggest using 3DES as the encryption protocol. RSA keys are prefered to passwords, but are slightly harder to set up.)
Click on the "advanced" button. You'll see a port forwarding tab at the top of the window; click on it.
You'll see a list of local port/remote system/remote port tuples. The ones you are most likely to want to tunnel are pop3 (port 110) for fetching emial, and smtp (port 25) for sending email. Click on new, enter the port/host info down below,and click on save. For me, the tuples are
110 krusty-motorsports.com 110 25 krusty-motorsports.com 25
IP addresses are also ok here. For something like accessing a MySQL database, the tuple would be
3306 krusty-motorsports.com 3306
Once these settings take effect, restart securecrt. Go back in to the session properties tab and make sure that the port forwarding list is still there. Sometimes in securecrt 3.0 I have trouble getting these to "take", and a couple of tries are involved.
Next, you need to change settings in your email client. Instead of containing the name of the server, it should now refer to 127.0.0.1 (localhost). This is because locally ssh is listening on 110 and 25 for pop3 and smtp connections and will forward them back to the server.
The only new restriction introduced by this setup is that you must have an ssh session running back to the server when you do pop3 and smtp transactions, which turns out to be no big deal.
Richard Welty / Krusty Motorsports / email@example.com