I am having an irritating Thunderbird problem that I can’t figure out how to fix. Any suggestions would be appreciated. In the past I have used different email addresses – for different purposes as my return email address. I would just click on the dropdown and I would then click on the one I wanted to use and then send the email – no problem. Of the three return email addresses only one of them was the same address that appears as my account name address that appears when I open “Account Settings.” In “Account Settings” I use one of my alternative email addresses in both “email address” and “reply-to address.” Recently, when I try to use one of the other two email addresses, and I click “send” I am getting the following message: An error occurred when sending mail. The mail server responded you are not authorized to send mail as: [email protected]. Please verify that your email address is correct in your account settings and try again. When I then switch to using my account settings name address the email is accepted. So what can I do to allow me to use all three email addresses at any point?