First, open your Profile folder:
       At the top right of the Thunderbird window, click the menu button New Fx Menu , then select Help, and then Troubleshooting Information. The Troubleshooting Information tab will open.
       Under the Application Basics section, click on Show in Finder. A window with your profile folder will open. 
   Close Thunderbird.
   Open the Mail (or ImapMail) folder in your file manager (according to whether you are using POP or IMAP with the affected account).
   Open the folder with your incoming mail server name (something like imap.googlemail.com or pop.googlemail.com).
   Select the Trash and Trash.msf files and delete them. In some accounts, these may be named Bin or Deleted.................

When I try to delete multiple emails in the bulk folder or the inbox a pop up appears saying the following the current information on bulk mail or inbox (depending on what file I'm in) did not succeed. I've already tried: f you cannot delete messages in Thunderbird, it may be caused by a corrupted trash folder. Here is how to delete the corrupted trash folder and create a new one: First, open your Profile folder: At the top right of the Thunderbird window, click the menu button New Fx Menu , then select Help, and then Troubleshooting Information. The Troubleshooting Information tab will open. Under the Application Basics section, click on Show in Finder. A window with your profile folder will open. Close Thunderbird. Open the Mail (or ImapMail) folder in your file manager (according to whether you are using POP or IMAP with the affected account). Open the folder with your incoming mail server name (something like imap.googlemail.com or pop.googlemail.com). Select the Trash and Trash.msf files and delete them. In some accounts, these may be named Bin or Deleted................. With no success. Thanks for your time