As (I believe) many OSX fellas, I connect my Google calendar with OSX calendar to receive all the notification in pop-up form – and just to have all the event a tap away. However when event reminder fires, OSX Mail app starts jumping in anxiety, yelling “Oh! Oh! You forgot to add your email! Do it, do it now!” – and that’s annoying because, well, I don’t use that app and I have no intention to.
The solution is simple (for a downside, read on):
sudo chmod 000 /Applications/Mail.app/Contents/MacOS/Mail
that’d just disable Mail app from being able to launch. It’s dirty, yes – but it’s that famous “good enough” kung-fu. If you need to get Mail app back to launchable state, well, just undo the spell with 755 permissions.
Now on that downside: you have to do this with each system update, because either app access rules or file itself get restored on update – that’s how I got to writing this, because I faced the problem again after an update. How to cope with it? Well, just do it again – updates are seldom enough. That’s how I’m gonna deal with it anyway.