Mozilla Thunderbird Problem

[RikuoAmero]

Okay, I've been using Thunderbird for a while now to keep track of my numerous email addresses. I have a separate email for each website or online service I use. This way, if someone hacks say my Facebook account and somehow also gets at the email used for that FB account, all my other accounts are still safe. All my separate emails point to one master email address which is where password reset requests are sent to, and that master email has another address to send its own password reset request to (this last master I have never written down on any website, so as far as I can see, it'd be quite difficult if not downright impossible for someone to hack it without knowing the address).

Anyway, for a few months now, Thunderbird has been retrieving emails for that first master like it should but every so often, it'll pop up with a message saying "New X amount of emails" and I go into it...but all the "new" emails are days old. I'm looking at it now, says there are 19 unread emails, and some of them are from back in May.

I check every single email address every single day. Thunderbird is the first program I start when I boot windows. So, anyone know why it constantly does this, retrieving emails weeks late?