Receiving emails isn't that hard. But that's not all you're getting into.
Sending them such that they don't get spam-canned is way more difficult than you're admitting. It can take months or years to get decent accept rates, all of which can be lost by a simple misconfiguration.
Parsing received emails if you want to do anything programmatic with them is also very difficult. The specs for email are vague, and even then many providers break them regularly. Want to strip quoted replies or signatures? Now you have a machine learning team, too.
Simply put, sending and receiving email is way cheaper to pay someone dedicated to the task to do. You have to get to a very large scale before it's worth doing yourself.
Sending them such that they don't get spam-canned is way more difficult than you're admitting. It can take months or years to get decent accept rates, all of which can be lost by a simple misconfiguration.
Parsing received emails if you want to do anything programmatic with them is also very difficult. The specs for email are vague, and even then many providers break them regularly. Want to strip quoted replies or signatures? Now you have a machine learning team, too.
Simply put, sending and receiving email is way cheaper to pay someone dedicated to the task to do. You have to get to a very large scale before it's worth doing yourself.