Also beware I tried this and it reset every single one of my emails in all folders as unread...

Yes, sorry about that, I should have made it more clear what the effects of applying this hint would be.
The Table of Contents file contains all the information about that particular mail box, except the messages themselves. It holds information about read, unread, flagged etc. It also contains the IDs of messages that have already been downloaded, which earlier versions of Mail.app kept in a separate file.

For what it's worth, the POP protocol was never designed with keeping messages on the server in mind, and as such all mail clients (such as Mail.app) use various workarounds to get around this problem - it works most of the time, so people come to rely on it... POP was originally designed so the mail client could log in, check for messages, download and then delete them. Having said that, I keep my messages on the server for a week. Now, when I did this procedure, it didn't download all my read messages again - I'm not too sure what I would have done different.

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k:.