Amazon.com Inc. ramped up the number of Halloween marketing emails it sent in the second half of October, email marketing vendor eDataSource finds in an exclusive analysis for Internet Retailer.

Amazon sent a total of 52 Halloween emails between Oct. 1-31  to an average of 829,000 consumers per send, compared with sending only six Halloween emails between Oct. 1-11 to an average of 291,000 consumers per send, according to eDataSource.

“Because Amazon is so sophisticated at managing customer contact, I suspect [the retailer] knows exactly whom to target—its campaign quantities suggest highly targeted messaging—based on prior purchase behavior, and exactly when those customers are most likely to become receptive to Halloween-related messaging,” says John Landsman, director of strategy and analytics at eDataSource.

Amazon’s average Halloween email open rate was among the highest, at 20.8%, of the Halloween-focused retailers eData source analyzed. Tipsy Elves LLC had the highest Halloween email open rate at 21.8% on average and Costume SuperCenter and Costume Express both had high open rates of above 19.0% on average compared with the other retailers.

EData source defined a Halloween email as a message that used any of these words in the subject line: Halloween, costumes, boo, trick, witches, scary, fright, ghosts, goblins or haunt. If the retailer has the word “Halloween” or “costume” in its name, such as “Costume Express”, all of its emails were considered Halloween oriented. EDataSource analyzed the subject line, open rate and volume send of email marketing campaigns between Oct. 1-31 for 16 online retailers that sell Halloween-related products including:

Many of the marketing emails touted aggressive price discounting, Landsman says. For example, one of Amazon’s top-performing Halloween emails referenced discounts of up to 63% in the subject line. Retailers promoted heavy discounting throughout the Halloween period, not just at the end, he says. Amazon’s highest Halloween email open rate was 66.7% with the subject line, “Halloween is Coming! Don’t Forget To Dress UP!!”

Interestingly, Target Corp. sent just one Halloween-specific email to 47 million people, which is a high percentage of its overall email audience, Landsman says.

“In the past we have also not seen Target jump as heavily into Halloween as we might have expected,” he says. “Target sent lots of other email during this time, some of that may have contained Halloween-related content other than subject line.”

Home decor retailer Grandin Road meanwhile sent no emails in the first two weeks of October, but four Halloween emails in the last two weeks, and on average, those four emails those had the fifth-highest open rate at 18.3%.

Landsman also notes that Halloween Express had a 25% inbox delivery rate, meaning that 75% of the time, its emails landed in a consumer’s spam or junk folder. This could be the reason why the retailer had a “dismal” average open rate of 6.0%, he says.

Halloween Express might have had inbox issues because of poor email address acquisition, such as not getting enough legitimate email addresses, and poor opt-in practices, meaning consumers may not be actively choosing to be on the email list, and list maintenance issues, such as not ensuring email addresses are valid or updated, and removing unresponsive users after six months to a year, Landsman says.

Brad Butler, chief operating officer at HalloweenExpress.com, disputes these numbers and says the retailer’s inbox delivery rate is more than 60% for mobile inboxes and more than 50% for desktops. The retailer uses a combination of internal and external sources to execute, manage and maintain our email marketing promotions, Butler says.

“It can be difficult to maintain high deliverability rates when you’re sending out millions of emails a week over the course of 60 days,” Butler says. “More importantly, email marketing continues to have the highest ROI of any marketing tactic we use–and by a wide margin. So on balance, we’re pleased.”

The other 15 retailers had what eDataSource considers a normal inbox delivery rate of about 85%-90%, Landsman says.