S-mail is like e-mail, but there is no body, and the entire message is conveyed using only the subject line.

Usually practiced using mobile devices (Blackbery, etc)
here's an example of a typical S-MAIL converstaion.

From: Johnny
To: Mary
Subject: Want to hit McDonald's for lunch?

<EOM>

---

From: Mary
To: Johnny
Subject: Sure, what time do you want to go?

<EOM>

----
From: Johnny
To: Mary
Subject: Let's go at 1:00

<EOM>
by Dooley Noted February 14, 2009
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Abbreviation of Snail Mail, referring to postal mail delivered by angry men in blue shorts.
“I got an extra print of that roller coaster snapshot, want it?”
“Yeah”
“What's your S-mail?”
by Najintrigue July 13, 2010
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