Strange feature of built-in email app on iPhone?

Question

iPhone

Interested in the pitfalls of the built-in mail application in iPhones. What confuses me is that once I once sent a letter to a colleague by mail (from a computer, Windows), then I discovered that the iPhone automatically entered the colleague's mailbox address in the additional contact information section in the phone's address book, added mail directly to her phone number . When you try to write a message to this contact, it offers either by SMS or by mail. How then did it happen at all? And only with this colleague such garbage, more than this was not with anyone.
In general, I don't like it. I just want to create a new mail, but I don't want all my cellular contacts to have it as well. What is this stupid app even doing?
PS colleague is not added to my contacts in Google mail itself. All I had was her number on my phone.

Answer 1

This is a feature. I also often add additional information about contacts, which is convenient.
Surely this can be turned off, google it.
But this is not a glitch.