We've seen some pretty strange intellectual property litigation in our day. We can now check off one of the dumbest IP lawsuits we've seen in a while. That's because Citigroup and AT&T resolved a trademark dispute Monday concerning how they each said thanks to their customers.

Banking behemoth Citigroup had trademarked "THANKYOU" and then sued AT&T over how the technology giant thanked its own loyal customers. Citigroup called it trademark infringement, amounting to "unlawful conduct" in a federal lawsuit lodged against AT&T this summer.

A federal judge ruled she wouldn't block (PDF) AT&T from thanking its customers pending a trial. US District Judge Katherine Forrest of New York also ruled that Citigroup likely wouldn't win at a trial. It's essentially a dispute in which AT&T is being accused of creating consumer confusion because it says "THANKYOU" in a manner similar to how Citigroup says "THANKYOU" to its customers.

We're not making this up, either. Here's a copy of Citibank's lawsuit (PDF) lodged in June. Here is a copy (PDF) of the trademark certificates and trademark applications connected to what Citigroup is calling its "THANKYOU Marks."

And not to be outdone by Citigroup, AT&T applied (PDF) to trademark the phrase "AT&T Thanks" and lodged a counterclaim (PDF) against Citigroup.

Counterclaimant AT&T seeks declaratory relief from this Court to prevent Citi from attempting to monopolize for its own exclusive use the common English phrase “thank you.” Citi claims to own a number of THANKYOU-formative marks, and asserts that its ownership of these alleged marks entitles it to prevent AT&T from using the word “thanks” for products and services in an industry wholly unrelated to Citi’s credit card business. In particular, Citi alleges that AT&T’s use of AT&T THANKS for its customer appreciation program infringes Citi’s rights in its alleged marks.

Both sides on Monday seemingly came to their senses on this issue and have agreed (PDF) to drop the litigation.