When attempting to download your mail, you may receive an error message that says "This folder is being processed. Please wait until processing is complete to get messages." There seem to be a variety of things that can cause this. Some are listed below, with links to threads offering further details and possible fixes.
- 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). Related information: see Bugzilla Bug 260447.
- Your anti-virus software locking up your Inbox. Also see this article on using Thunderbird with anti-virus software.
- 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.
- Accidentally double clicking "Get Mail", accidentally clicking "Get Mail" while trying to select an account from the adjacent drop down list, or the PC resuming from sleep mode can cause this. There are a lot of other variations, what they have in common is that they're all timing dependent.