User Agent: Mozilla/5.0 (X11; Linux i686; rv:19.0) Gecko/20100101 Firefox/19.0 Build ID: 2013021500 Steps to reproduce: 1. Write an e-mail; choose Send Later from the File menu. 2. Choose "Send Unsent Messages" from the Outbox context menu. Actual results: The SMTP server I use has some limitation which does not allow many e-mails being sent in a row and when the limit has been exceeded, sending another e-mail with Thunderbird gives an error dialog box like this: "An error occurred while sending mail. The mail server responded: 5.7.1 <john.smith@example.com>: Recipient address rejected: 0. Please check the message recipient john.smith@example.com and try again." Now the outcome seems to depend on how fast I click on the OK button in the error message dialog: a) if I click the OK button fast enough (less than a minute) then the e-mail remains in the Outbox and is not copied to the Sent mail IMAP folder; b) if I wait longer (e. g. three minutes) then after clicking OK I see that the e-mail has been removed from Outbox and copied to the Sent mail IMAP folder, leaving a false impression that the e-mail has eventually been sent (which is not the case). Expected results: Outcome a) should happen no matter how much time passes between displaying the error message and clicking OK.

"mail in Outbox" version of bug 780124. Setting dependency.