Thunderbird - Red Exclamation Mark on Recipient Address in Compose

Problem:

Red exclamation mark next to an email address in the compose box. Originally I copied the email address from OSTicket. It looked like this "test@aol.com" with bold on the "t". This was the invalid character. Strange because now I can't reproduce it.

Resolution:

There's a non-windows character in the name somewhere. Try typing the name in directly vs copying and pasting the address from another program.

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