Speed Issue with Large Mailboxes

[Fuzzle]

Heya,
My "Family" subfolder on my server has around 1200 messages in it. With Outlook express, this was no problem, but now with Minny/Tbird, it takes forever to load it. I click on it, and it just sits there saying "opening folder" for a little while. I made my own "Custom view" that only shows unread messages and those from the last week, and this helped, but what I was wondering was if this was a known issue with the way that Moz interacts with the mailserver or what...

Just thought I'd ask..