-------------begin config----------------

NameVirtualHost *:443

<VirtualHost xxx.xxx.xxx.xxx:443>
    ServerName webmail.your_domain.com:443
    DocumentRoot /usr/share/squirrelmail
    ErrorLog logs/webmail-error_log
    CustomLog logs/webmail-access_log combined
SSLCertificateFile /etc/httpd/conf/ssl_certs/your_cert.crt
SSLCertificateKeyFile /etc/httpd/conf/ssl_certs/your_key.pem
SSLEngine on
SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP
</VirtualHost>

---------------end config---------------

where xxx.xxx.xxx.xxx is the IP address you are listening on

your_cert.crt is a certificate for your site

your_key.pem is a private key ... with the password turned off ... for your site.

here is a guide to help you build certificates:
http://slacksite.com/apache/certificate.html