No Sooner Do I Post...
Literally as i clicked submit on my last post, my Mail icon in my dock lit up with a tell-tale "2". I use a company called E-Junkie to handle paypal processing for me. For 5 dollars a month, they shield me from the vagaries of paypal's IPN API. This is a terrific value, and i'm incredibly happy with their service. A quirk of using E-Junkie on top of paypal is that i receive two emails whenever i make a sale. Thus, whenever i see a "2" (or really any number > 1) on my Mail icon i get positively giddy. The moment i clicked submit, Mail checked all of my accounts and lo and behold, i had a new customer for MercuryMover.
As an aside, does anyone know if there is some Mail/Safari mojo/notification that makes Mail check all accounts whenever you submit something in Safari? I actually really like this feature; it's useful when you sign up for something online and receive your email notification immediately.