So currently you have:
http://www.mydomain.tld/webmail
and you want to reach webmail via
https://www.mydomain.tld/webmail
as well?
Since webmail is an alias (points to a Directory directive), you would need to config a global SSL setting so you can reach ALL website with or w/o SSL ..
if you run one domain on it and want normal/ssl connections to the website and the webmail alias, just copy and paste your existing VirtualHost, change the port to 443 and add the SSL options, save, restart, done.
