Ubuntu – Where is the delete account button in Thunderbird on Ubuntu 12.04

In Thunderbird, go to EDIT, ACCOUNT SETTINGS. Go to the bottom left and Select OUTGOING SERVER (SMTP). Click add to add your wanted server if it's not in the list.

Next scroll back up and click on the account you want to modify. In the bottom right, select the outgoing server you want for that account.

Yes. There is a way to do this using the config editor.

The source for this solution is a post by user billko at http://forums.mozillazine.org/viewtopic.php?f=30&t=1463325 however users of current Thunderbird version may get confused with the steps provided in that post (as I was) hence this Q&A. This will also be useful for Ubuntu+Thunderbird users who look for solution here.

• Open Thunderbird Mail
• Go to Edit > Preferences > Advanced
• Click on 'Config Editor' button
• Agree to the warning
• In the search box type account
• In the list of options displayed, look for the email addresses and identify the accountn vis-a-vis the servern vis-a-vis the mailbox, where n is a serial number in the order in which the account was created (see image below)
• Now edit value against the preference-name mail.accountmanager.accounts to reflect the sort order you want
  eg. in my case, I modified the original order account1,account2,account3 to account3,account1,account2
• Now also edit the value against the preference-name mail.accountmanager.defaultaccount to the first account in the sorted list as above
  eg. in my case, I set it to account3

Image: Thunderbird config editor - account sorting