As you’ve probably heard, an overwhelmed UPS had a lot of trouble making deliveries before Dec. 25 this year. And the results of a national test of online retailers show that these delayed deliveries were not relegated to just a few major sellers.

After first figuring out the ordering deadlines of the country’s biggest online retailers, the folks at StellaService then placed multiple orders — with delivery addresses in different regions of the country — from each of the websites.

According to their results, eight of the 25 retailers tested — Staples, Dell, TigerDirect, Kohl’s, Macy’s, Pottery Barn, Nordstrom, Gap — failed to make good on getting all of the purchases delivered by the deadline.

But while the late deliveries represented a range of retailers, all but one of the missed shipments was handled by UPS.

One company cited by StellaService as going above and beyond was Zappos, which not only pushed the limit by having an ordering deadline of Dec. 23, but upgraded last-minute shoppers’ delivery options to guarantee the packages arrived in time for Christmas. Of the retailers with a Dec. 23 deadline, Zappos was the only one to get all of its parcels delivered on time.

You can see the full results of the test at StellaService’s Happy Customer blog.

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