E-mail is unreliable
Having worked on various projects where e-mails were used I came to this exact conclusion. E-mail is unreliable, as a medium.
It is not obvious while coding it happily, but certainly gets painful after doing maintenance over an application for a prolonged period of time.
“I’ve sent an e-mail and now it’s not my problem” attitude, assumption that an external component always works, will bring trouble to the final product.
Let’s look at using e-mail in the app-wide, business-wide perspective.