Kinda… you do need to enable it in settings.

Honestly - don’t. Not unless you intend to be their 24/7 tech support…

I learnt this the hard way when I worked out my shutdown script that did this automatically had stopped working :P

True, but it presumably would still require the user to open them.

But, I was mostly worried that just having the server installed would be enough.

It’s only if you view a specifically crafted email in the web client… still worth upgrading of course.