Sometimes when I am composing an outgoing e-mail, the address that I type in the Addressee field shows up in red, and sometimes it shows up in black. This is on Thunderbird 38.3.0, but has been happening with the last several versions. I originally thought that red meant that either (a) the address is not valid as typed in, or (b) the address is valid, but not present in the Address Book. However, now it seems that red shows up randomly and fairly often, even though the message is a Reply (and I do have automatic collection of addresses turned on) or even though I know for certain that the address is present in my Address Book. Can anyone explain what the color is supposed to mean? (Of course, now that I have raised the issue, I can't reproduce it today to give you a screen shot. But it has been happening.)