Thats where a wildcard ssl comes into play. Wildcards are *.url.com, meaning they can cover anything and every that is before your domain. you'd use a wild card for url.com, then the wildcard for mail.url.com, or dev.url.com, etc
Youd need to install the wildcard on various servers still, like it doesnt auto pick it up. If you were using lets say apache to host your website, youd have to install the ssl on the server and make sure your config files pointed to it. Also if you used a system that runs proxies such as haproxy or nginx youd have to point those config files to the ssl. Then if you ran a mail system (for brevity lets just say exchange) the ssl would need to be on that server and set up for it.
If its a simple system with one server, its mainly just pointing config files to the ssl.