Import imports mail from POP mail account. There is an expectation that IMAP mail will be re-downloaded from the relevant mail server.

Hi, Thanks for the reply, but I'm confused. When I delete a message it gets deleted from the server. And one of the accounts that only imported the headers is a POP3 account. Why didn't the POP3 account import the message content? There must be something else going on.

This issue has been resolved, but the root cause was never identified.

I found that the Postbox mailbox files were imported to Thunderbird intact. That is, they contained both headers and contents of all emails from all accounts. In spite of this, I could determine why TB was only displaying the headers and not the contents.

Since I seemed to have run out of ideas, I simply opened each mailbox file (inbox, sent, etc.) and any associated .msf file, in Postbox, by using Notepad. For each mailbox file, I copied the contents of each Postbox file. I then opened the same mailbox file in TB, deleted the old contents and pasted in the copied contents from Postbox. I did this for each mailbox and .msf file in each account. After the copying was completed, I opened TB and everything was now displayed.

As I said, I do not know why this worked. The files imported by Thunderbird from Postbox were identical in size right down to the byte, so should have been identical in contents, but there was something that manually copying the contents provided that the TB import utility did not.

I'm now going to sit in the closet for awhile.