Error: "Unable to open summary file..."
If you are receiving the following error:
"Unable to open the summary file for [folder name]. Perhaps there was an error on disk, or the full path is too long," then you could have a corrupted mail index file.
Please go to the Postbox "Help" menu and select "Trouble Shooting..." and then select this option:
_X_ Reset IMAP mail databases and Search Indexes
Then restart Postbox.