(US citizen, spouse of Japanese National) Just received COE, do I need a letter of guarantor?

I can’t find a clear answer for my situation, I’m living in the US with my wife currently.

Website doesn’t mention needing one.

(https://www.mofa.go.jp/j_info/visit/visa/long/visa10.html)

Also are mail in applications accepted or do I need to travel to my closest embassy?