With a bit more investigation the change seems to be that Thunderbird used to pass a temporary file (e.g. c:\users\jfd1\appdata\local\temp\tmpdj7m7c.eml ) that remained in place after the drag and drop. Now the temporary file is deleted after the drag and drop so task coach cannot find it again.

This is odd as in the past Task coach used to get the mail direct from the imap server (it required to know imap credentials).

You say that the problem is that the file saved in "c:\users\jfd1\appdata\local\temp\" gets deleted, which is causing the problem.

That folder is a temporary folder for use with your Windows user. Windows and other programs create files there that are not supposed to stay there for long. Ideally, the files saved there are deleted by whatever program created them, as soon as they are not needed anymore. It is temporary folders like this in Windows that tend to become bloated over time, and need to be cleaned out, using tools like Windows Disk Cleanup, and CCleaner.

When you drag and drop an e-mail from Thunderbird onto "Task Coach", Task Coach then decides what to do with that e-mail. What Task Coach is doing is saving it in the Windows user temporary folder, when it should be saving it in a folder for use with just Task Coach for longer term storage.

Thanks for the input. This pretty much confirms what I suspected. I presume the current version of Thunderbird cleans up after itself whereas the earlier versions did not. I'll work on getting TaskCoach fixed :)

It is not Thunderbird is not cleaning up after itself that gets rid of that file.

Again, it is Task Coach that creates the file, and Task Coach that deletes the file.

Having investigated further, on dragging a mail message to Task coach: Thunderbird 45.8.0 definitively passes Task coach a url of the form:

 imap-message://fred%40gmail.com@imap.googlemail.com/INBOX#69

The e-mail is then retrieved from the imap server by Task Coach and stored internally in task coach's database. It is also stored in a file in c:\users\fred\appdata\local\temp\ so that it also be opened by an e-mail client.

Thunderbird 52.2.1 passes a filename of the form

 c:\users\fred\appdata\local\temp\tmps8yrzm.eml

By observing with "PA File Sight" file activity monitor, this is a file written by Thunderbird at the start of the drag and drop, and then deleted by Thunderbird at the end of the drag and drop. Task coach only stores the file path for file drops so the e-mail is lost to it.

So Task coach no longer correctly catches dropped mails from Thunderbird 52.

If anyone knows how to switch Thunderbird back to giving an imap URL that would enable me to fix the problem. I expect Task coach may be fixed to correctly catch the file, but at the moment my Python skills are not up to the task.

I have posted a fix at: https://sourceforge.net/p/taskcoach/support-requests/465/