A "blast email" refers to sending the same message to a large group of people all at once. It is often used for advertising or sending out important information quickly and efficiently. Full definition
And when some people inevitably stop opening blast emails altogether? (epolitics.com)
Marketing agencies will send out blast emails when work is available in your area. (thecollegeinvestor.com)
The latest example showed up in a recent blast email from Patrick Riccards, ConnCAN's CEO and head cheerleader for Governor Malloy's «Education Reform» bill. (jonathanpelto.com)