We've been examining email marketing trends on major shopping occasions throughout the holiday season. So far we've looked at Black Friday, Cyber Monday, and Green Monday. Next up: Free Shipping Day.

A Shopping Occasion in Decline
This year 73% of the more than 100 major retailers that we track sent their subscribers at least one promotional email on Free Shipping Day, which was on Dec. 18 this year. That's down from 77% last year. This current level of activity made Free Shipping Day a decidedly average email marketing day during the holiday season, whereas last year it had been above average.

Perhaps more importantly, only 9% of the promotional emails sent by retailers on Free Shipping Day mentioned it by name. That's not to say that there weren't plenty of free shipping offers to be had, but that's not all that unusual these days-which is a big part of the problem for Free Shipping Day as a brand.

The Commoditization of Free Shipping
Back in 2008 when Free Shipping Day burst on the scene, free shipping was still a huge draw because it wasn't offered all the time. However, over the years, more retailers now have standing free shipping offers all year long, and others offer free shipping for the entire holiday season. That's why I predicted we'd see more "free gift card with purchase" offers this holiday season, which we totally have.

Ultimately, trumpeting Free Shipping Day causes confusion, since it implies that you don't generally offer free shipping and it also often means that it's the last opportunity to get free delivery in time for Christmas. For these reasons, most of the small percentage of retailers that promote Free Shipping Day do so because it coincides with their shipping cutoff for guaranteed delivery in time for Christmas using standard shipping.

Because of all of this, not only are fewer retailers promoting Free Shipping Day, but fewer consumers are searching for the term, according to Google Trends data. Searches for "Free Shipping Day" peaked in December of 2010. Compare that to the number of searches for "Green Monday," which was three times greater than those for "Free Shipping Day" this year.

With search being the faster, leading-edge channel, I expect that email marketers next year will mention Free Shipping Day even less - and Green Monday much more.

This post originally appeared on the Salesforce Blog.