index failed

When reindexing I go the following error

Mailbox test: UID=1: read(/path/to/mail,S=4248,W=4349) failed: Cached message size larger than expected (4248 > 1182, box=test, UID=1) (read reason=mail stream)

In this case, the message was an unimportant test message with no content, so I simply removed it, but had it been important what would I need to do?

-- Nine-tenths of the universe is the knowledge of the position and direction of everything in the other tenth. Every atom has its biography, every star its file, every chemical exchange its equivalent of the inspector with a clipboard. It is unaccounted for because it is doing the accounting for the rest of it. Nine-tenths of the universe, in fact, is the paperwork. --The Thief of Time