Ability to enable entities for emails is great – it’s another useful slice of functionality previously reserved only for contacts and accounts. If you are like me and prefer a minimalistic approach to entity design, you may be tempted to check the box enabling emails and be done with it. This is not going to work well, unfortunately, without enabling activities as well:

It’s one of those things that make total sense when you think about them: emails that you are about to send are activities, right?

Thanks to my good comrade Oleksandr “Salo” Klymenko for the tip!