An overwhelming amount of email; an email deluge. Also: e-mailstrom, mail-strom. [(e-)mail+maelstrom.]
Maelstrom: a restless, disordered, or tumultuous state of affairs
Mailstrom: where email is the source of that restless, disordered or tumultuous state of affairs...
There are real advantages to email, and incorporating the risk management tips into your personal and firm email routines will help you enjoy the benefits while staying safe from the "mailstrom."
—"Email: Preventing a mailstrom," The Law Society of British Columbia, October 26, 2009
The White House does not comment on security matters and so wouldn't say how Bush's mail is tested. Nor would officials there comment on a practice employed by earlier presidents: telling certain friends and family to put a unique numeric code on their envelopes so the letters wouldn't get lost in the maelstrom (or mailstrom, yuk-yuk).
—John Kelly, "Answer Man: A Presidential Paper Chase," The Washington Post, July 5, 2004
They've built in protection against chaotic "mailstroms" that could result when agents trigger each other to respond in mad exploding loops.
—Paul Somerson, "E-mail bonding," PC-Computing, August 1, 1994
The variation e-mailstrom is slightly older, with the earliest citation being a Washington Post headline from July 18, 1994: "On to the Internet and Into the E-Mailstrom — Painlessly." Note, too, that a Mac email program called Mailstrom first appeared in 1992. Many thanks to Anne Marie Koper for alerting me to this word (by coining it independently!).