Well I certainly don't want to promote printing of emails from your phone but I'm sure sometimes you really do need to print out your email on hardcopy.
Apple has built in a feature called AirPrint that allows you to connect your printer wirelessly to your phone but it only works for a very small subset of modern - very modern printers.
Certainly mine doesn't support it. I've had my printer for seven years now and it's still working great. I can make it work however using a product called PrintTopia. Printopia is an add-in on my Mac which allows me to wirelessly connect my phone or iPad and print from the device.
So if you have a modern printer that supports it check out using AirPrint. it's an Apple provided facility. if you don't check out the product called PrinTopia which allows you to use any connected printer on your Mac as an AirPrint device.