Consumers aren't just ignoring your holiday emails. Some are saying "Bah, humbug!" and avoiding them altogether by creating multiple email identities to filter messages.

Nearly 50 percent of email users surveyed maintain at least three addresses to protect themselves from spam and other e-commerce threats, according to a study released by Habeas, a provider of email reputation services. The study, released in October, also found that 81 percent avoid forwarding multiple accounts to central addresses.

Habeas calls this behavior the "email insecurity factor"and warns that it presents serious implications for any retailer that uses the channel to entice buyers with sales, promotions, discounts and other special offers.

"We have to be cognizant that consumers are empowered to vote on how they feel about a brand online," says Habeas CEO Des Cahill. "And it's easy for an enterprise to run afoul of consumer willingness to engage in a dialogue."

Survey respondents cited the inconvenience of spam, safety/privacy threats, and a lack of confidence in existing solutions to counter these problems as the drivers behind the decision to hide behind multiple email accounts. Of those surveyed, 62 percent expressed concern about fraud and 60 percent agreed that spam is becoming worse.

Most disturbingly for retailers, the practice of keeping several in-boxes is more prevalent among younger consumers. Survey respondents who were under 45 years old were 9 percent more likely to use multiple email accounts versus those who were 45 or older.

More than 50 percent of those with two or more email addresses cited trust or privacy as their reason for keeping separate accounts. Consumers are creating "more trusted and a less trusted in-boxes" says Cahill. He says they create one for work, another for friends, family and trusted brands, and one for signing up for online offers and lists. Doing so allows consumers to protect themselves from unwanted communications and to put emailers through a "trial period" before they elevate them to trusted status, according to Cahill.

Email continues to grow in importance as a marketing channel. US marketers will spend $500 million on email marketing in order to post $21.9 billion in sales this year, according to the Direct Marketing Associations. Much of that volume will come during the all-important holiday shopping season between Thanksgiving and Christmas as retailers coax consumers to open up their wallets and spend, spend, spend.