Canada

Huh, I never thought about this. The plurality norms don't quite match snail mail.

• "The mail is here" (this sounds normal)
• "The mails are here" (this sounds unusual)
• "I got an email" (this sounds normal)
• "I got a letter" (this sounds normal)
• "I got a mail" (this sounds unusual)

I guess this comes down to the fact that there is no widely-used word for a single piece of electronic mail. Perhaps "eletter" would be the analogue, but I've never seen it used. As a result, "email" is used for both a single piece, and the category as a whole.