Largest Mail.app mailbox size?

I mentioned a couple of months ago that my personal inbox had crossed the 20,000 e-mail mark; I’ve now just passed 22,000.¹ I’m fairly certain that the app itself doesn’t have an upper limit, and so I’m curious to know, what’s the largest usable Mail.app mailbox out there (and by usable I mean a mailbox that’s being hammered on a daily basis)?

I’ll keep updating this post with the largest number I receive.

Currently, the largest number is 283,686 (I required screenshot proof of this one).


FOOTNOTES
  1. I’ve had a lot of people e-mail me about the fact that my e-mail doesn’t seem to be sorted in any particular order, but is instead all lumped into one big folder (or two, sent/received). This actually isn’t the case — I use Mail Act-On (something I’m sure to write about in the future) in conjunction with a fairly elaborate system of smart mailboxes (scroll down a bit after the jump), which leave the mail in its original folder, but replicate it across the smart mailbox.