Sort by Received Header
To sort messages by the Received date for IMAP accounts you need to do the following:
- Open the config editor.
- Type "mailnews.customDBHeaders" into the "Filter:" textbox
- Right click the entry and choose modify to append the value Received to the comma delimited list of extra headers to fetch from the IMAP server.
- Restart Postbox
- Rebuild the index for your INBOX.
- Add the Received header to your message list pane by right clicking on a message list column and selecting the Received header.