Hi, Don't think I understood the question exactly but I'll answer to what I understood. In thunderbird you can configure multiple mailboxes. For this you go to Tools>account settings>account actions (lower left hand corner) and add a new account. Each account is setup with its receive (POP3 or IMAP) settings and its send email settings (SMTP). When you receive an email in account A and hit reply it will reply by default using account A. The same goes for B. If you want to reply an email that you received in account A but you want it to be sent from account B, in the compose window you press the "from" where you see account A and it will show you account B as an option. Just select it. I hope it helped. Edo