In a nutshell: emails I send from mailbox abc.com are received as having come from mailbox xyz.com. And Thunderbird appears not to be using the default outgoing server. Details: I have email accounts with several different providers, each with their own outgoing server. I manage them all in Thunderbird, which uses one designated default outgoing server. I send and receive business and personal emails from different mailbox accounts. Because of the overly-aggressive spam filter at my main account's outgoing server, I recently changed the default in Thunderbird to an outgoing server associated with another account. I've noticed that since then, no matter which mailbox I send an email from, they all have the return address of the account associated with the outgoing server. Any replies come back to that mailbox only, instead of to the one I sent the email from. All my business and personal emails end up in that mailbox. So I've designated my original outgoing server as the default once again. But Thunderbird is still using the problematic outgoing server. The "From" bar at the top of the email I send lists the correct mailbox, but when I click 'send', the email is sent from the wrong one. And any replies I get come back to the wrong inbox. Please help. == I changed default outgoing mail server