When I tried to add my Gmail account, I was notified by Google with a message that follows:
Sign-in attempt prevented
Hi, Someone just tried to sign in to your Google Account from an app that doesn't meet modern security standards. Details: We strongly recommend that you use a secure app, like Gmail, to access your account. All apps made by Google meet these security standards. Using a less secure app, on the other hand, could leave your account vulnerable. Learn more.
Google stopped this sign-in attempt, but you should review your recently used devices.
Basically, right now there is no way to use Geary as a mailbox for Gmail (and for other services it, apparently, doesn't provide enough security). It's not really a question, but I would love to have this issue fixed.
Are elementary devs going to do something about that? If yes, when the update will be available?