Muaha. I was desperately trying to clear my Hotmail archived mail so it won't overflow so soon next time, and I clicked too fast in my fluster. In the end, I accidentally deleted the mail in Mozilla Mail before I'd moved it to another folder, though I'd saved all my messages in eml format.

Racking my brains, I've imported the eml files into Outlook Express, then imported them in Mozilla Mail.

Such are the little things in life :)