A lot of mail clients will do the right thing if a URL is enclosed in < >.

Meaning you email the URL as:
<http://www.server.com/cgi-bin/script/script.plParam1=Value&Param2=value&Param3=value>

If you still need to cut down the length of the URL, I would still look at just passing a session key with the URL and then doing a database lookup based on the key.

Also, rather than building the key lookup into the main cgi script, I suggest that you write a generic redirect script that does the look up.

Meaning, you send <http://www.server.com/cgi-bin/redir.pl?KKDIS47> and the script does a database look on KKDIS47 and then redirects to http://www.server.com/cgi-bin/script/script.plParam1=Value&Param2=value&Param3=value