Why do addresses appear in red and prevent me from sending my email? | Thunderbird Support Forum

07:40 14/12/2024

Usually a red font displayed in a 'TO' field means the email address you typed is not in any of your address books. It does not mean anything is wrong with the email address. The colour is used merely to draw your attention to the fact it is not in an address book. However, if you have not typed it correctly that is another matter entirely.