I frequently see two errors while using the Thunderbird email program. The first is:

There was an error truncating the Inbox after filtering a message folder to (folder name). You may need to shutdown Thunderbird and delete INBOX.msf “

Needless to say, deleting INBOX.msf had no effect, although that solution does work for some people so it may be worth trying first, just make sure you do NOT delete “Inbox”. Deleting all filters would solve the problem, but then I need my filters for the several dozen press releases I receive each day…so that’s no solution either.

The second error message is:

“This folder is being processed. Please wait until processing is complete to get messages.”

According to the Mozilla site this can be due to one or more of several problems and has been an unresolved bug in Thunderbird for several years now:

• Messages with bad headers or header fields left blank.
• Checking multiple accounts while filtering mail between accounts.
• For older (pre-1.0) versions of Thunderbird: simultaneously getting mail for two or more accounts that use the Global Inbox. In Thunderbird 0.8, it may be possible to avoid this problem by clicking the “Get Mail” icon in the toolbar rather than using the keyboard shortcut (not yet confirmed).
• Anti-virus software is locking up the Inbox.
• You don’t have permissions to read/write to your inbox. This can happen when sharing mail between linux and windows and the partition containing your inbox has been mounted with permissions higher than the user running Thunderbird.
• Checking mail while compacting folders for the account(s) being checked.

It was in looking for a solution to the second problem that it occurred to me that perhaps having upped the security level in Zone Alarm Security Suite so that it was running and scanning email that I could have inadvertently instigated problems. Once I’d disabled it, things were back to normal. Your mileage may vary.