I am building a CMS for my company(using Rails 4, in case that matters) and nearly all of my users will be using Gmail.
Each user has a profile and I want it so when a user views another user's profile and clicks on their email address, Gmail will open with a new message to that user's email.
I imagine there'd be a way to do this using their API but so far I haven't found it.
There's no way I know of to specifically open Gmail; mailto always opens the default mail client, which can be set to Gmail.
See this guide (or direct your users to it) so that they can set Gmail as their default client: http://blog.hubspot.com/marketing/set-gmail-as-browser-default-email-client-ht