Your first email should include "Metamath" in the subject to add you to my spam filter's whitelist.
When possible, I prefer plain text email (not HTML formatted).
As of September, 2018, Google seems to have put me on some kind of blacklist and has been bouncing many of my emails to gmail.com as spam. The following procedure to add me (nm at alum dot mit dot edu) to gmail's white list seems to have solved the problem in one case:
How to Setup a Whitelist in Gmail
I would recommend doing that if you email me from a gmail address (and want a response).
My postal address is:
93 Bridge St.
Lexington, MA 02421-7946
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