Should I SSH tunnel POP3s and IMAPs email connections

--- Helo ---
Should I set up an SSH tunnel for POP3s and IMAPs email connections?
Using PuTTY 0.58 and Thunderbird 1.06 I'm able to check email.
If I set up an SSH tunnel for the POP3s (or IMAPs) account and set Thunderbird's mail server name to localhost,
Thunderbird pops up a window like this:

Security Error: Domain Name Mismatch
Your have attempted to establish a connection with "localhost".
However, the security certificate presented belongs to
"mymailserver". It is possible, though unlikely, that someone may
be trying to intercept your communication with this web site.

If you suspect the certificate shown does not belong to
"localhost", please cancel the connection and notify the site
administrator.

Viewing the certificate, it does appear to be from mymailserver and I am able to check mail with this account by clicking OK.
The good thing about connecting to the email this way is that there is no separate direct connection to mymailserver, it all goes through the 1 SSH connection.
The bad things are that you have to click ok on the Security Error window every time I want to check email and if there ever was any real intercept "funny business", I wouldn't know the difference from a regular email check.

Is there a way to set it up so I don't get the security error and it still connects through the tunnel?

I can set it up without a tunnel and Thunderbird will connect directly to mymailserver with a separate secure connection (it works without getting the security error window and the connection is encrypted), but it still shows up as separate connection and reveals the mymailserver connection.