[KyleGoetz]

Originally Posted by sakaeyellow

If it is possible, please tell us more details and let native speakers here choose the best level of formality for you. As for the details, your ages are very important. If he is significantly older than you, you should not just call him by his first name in Japanese.

Motomoto is a native Japanese speaker and knew the letter was to a friend (it's obvious from the content of the email).

I recently wrote a letter to my hostmother using plain form, and she corrected my letter, replacing every instance of plain form with polite. She then wrote me a note:

Originally Posted by hostmother

手紙の時は「ました。」とか「です。」とかでおわるほ うがよいです。それがふつうです。