DA is a hosting panel. Gmail is a specific e-mail service.
One could use an e-mail client like Thunderbird which has PGP build in.
In my opinion it's up to the appropriate software developpers to provide such option.
So not the hosting panel, but for example Roundcube, as that is the webmail system. Or Exim to put mails encrypted in the mailboxes, or the e-mail clients (like Thunderbird does), so customers can choose whether or not to use encryptions.
So that is why my choice was no. I wouldn't know what DA would have to do with it. DA is basically just a shell for other applications.