"Christmas" or "Holiday"?

A marketing communications company has studied which email subject lines lead to the best open rates around the holiday season.

“Happy Holidays” is an inclusive greeting but it may not the best phrase for retail marketers to use in their emails.  Actually, emails with the word “Christmas” in the subject line  boast open rates 26% higher than those that use the word “Holiday.”  The word “Hanukkah” drives open rates 40% higher than “Holiday.”

I wonder why this is?  Does the mention of a specific holiday conjure up a different image in our minds (and thus slightly different feelings and emotions) than the generic word “holiday”?  Would this finding apply in other contexts like TV ads or in-store displays?