Now that GMail invitations are leaking more than the Hoover Dam and everyone’s getting their kicks off reviewing and teasing this new mail metaphor, we’re not done with the “War of the Emails”, not by far.

In one corner, we’ve got the encumbents defending their positions through categorical filtering. That’s right, both Yahoo! and Hotmail are blocking, I mean filtering, GMail invites into the circular file. Don’t believe me? Check out this tidbit from news.com:

Receiving a coveted invitation to open a free e-mail account on Google’s Gmail is a thrill that’s literally lost on Microsoft.

At least it was for Joel Johnson’s girlfriend, whose MSN Hotmail account (a rival free e-mail service) bounced invitations to join Gmail twice last Wednesday. That day, Johnson was given the chance to dole out two accounts for Gmail to friends before the high-profile service is widely launched, per Google’s policy of limiting membership to friends, and friends of friends, while it works out the kinks.

Source: News.com, “Hotmail giving cold shoulder to Google mail?”

And even though Hotmail hasn’t chosen to respond to the challenge, don’t think Yahoo! is giving up so easily. They’ve not only upped the ante, providing 100MB for free and 2GB for $20 a year, they’ve also changed the interface to their entire application.

I’ll be posting my GMail review soon.