I use Greek letters Omega (Ω) and mu (μ) in electronics discussion, where the Greek Omega (Ω) is the symbol for "ohms" of electrical resistance to the flow of current, and Greek mu (μ) stands in for "micro" or millionths of an ampere of current (1μA is 1/1000,000th of an ampere of current flow). I sent an email to others and my email account on which I use Thunderbird Mail (version 115.13.0 on Linux Mint). I artfully spelled in all caps the word "Communicator," using the Ω sign in the place of "O" and the μ sign in the place of a "U." I received the word with this spelling: "C?MM?NICATOR" Checking in Firefox on my Gmail account's Sent folder, I found the Greek letters in good order. Firefox can use UTF-8 encoding. I found a solved thread on the Stack Exchange. Look under Tools • Options, as it is in Windows, but in Linux that's Edit • Preferences • Display. I have neither Options nor Preferences in this version of Thunderbird, nor can I find anything about setting encoding in Edit • Settings. I should set encoding from Western to UTF-8 on both incoming and outgoing mail to see foreign characters. Some info about my installations of Firefox and Thunderbird here: In order to not lose my profile when I need to reinstall Linux for whatever reason, I have both Profiles stored on an outboard disk that is treated as a permanent disk on the system. This move also gives the profiles room to expand as needed Linux Mint 21.3 Cinnamon 64-bit MintBox Mini 2 Pro by CompuLab No longer on Amazon, but info [https://www.linuxmint.com/store_mintbox.php here at the Linux Mint store] . So I ask, "Where to from here?"