I think this is interesting. I have a feminine first name and have never received mail addressed to Dear Sir, so this was something I had never considered. (Aside, I have a grandmother named Genevieve who goes by Gen--she sometimes gets mail addressed to Dear General Lastname offering her military-related materials, which is pretty funny.)
https://corporette.com/2011/01/19/dear-sir-the-problem-with-gender-neutral-names/
Re: Interesting Discussion of Gender Neutral Names
My husband and I have a similar issue with our last name. My husband is part chinese, and we have a Chinese last name. People always assume I'm an asian woman (I have blonde hair and blue eyes).
Mind you, neither one of us speak ANY chinese, and both grew up in California. We constantly get mail sent to us printed only in Chinese, that we can't read. At first it was hilarious but now it is just annoying.
Interesting. I have a gender neutral name (with several variations on spelling) and I've never recieved anything addressed to Mr. ____. It's actually never been a problem. Other than in first grade when there was a boy with my name in my class, and the other kids laughed because we had the same named (spelled differently).