how do I remove “sent from iphone” from email messages sent through my iphone

Settings->Mail->signature

It's a default signature. Go to Settings/Mail and scroll down to Signature. You can edit the signature there and make it anything you want. If you have more than one email account you can also create different signatures for each one.

Tap either All Accounts or Per Account. If there are no signatures create one and don't put anything in it; just a space.