Dear evolution, you are on crack.
Time to ‘filter new messages on my imap store': ~ 5 minutes.
Number of new messages? 6.
Ability to access already-cached-for-offline messages during this period? None.
Frustration because I can ssh home and cat /all/ the new messages, and determine they are spam, and their folders, in less time: Priceless.
Oh, and DNS is fine – a little slow (4 seconds to determine example.org), but working.