Companies and other entities that own trademarks regularly monitor third party use of what those entities deem to be confusingly similar marks, in an effort to police their trademark and maintain trademark rights. In doing so, it is fairly common for trademark owners to send a cease and desist letter. They send these to anyone making use of a mark that they believe will lead to a likelihood of consumer confusion, which is the test for trademark confusion under US law. If you receive a cease and desist letter from a trademark owner, there are certain steps you should always follow in order to protect your rights.
First, if you are in a position to retain a trademark attorney you should immediately contact your trademark lawyer, who can review the facts and laws specific to each matter. Trademark law is a very fact specific area of law that requires analysis of the trademarks at issue, and a detailed analysis of the likelihood of confusion factors available for assessing these kinds of matters. If you are unable to retain legal council, you should still educate yourself about what options exists.
Second, you should identify whether the trademark owner indeed has a protectable trademark. You may search the US Patent and Trademark Office database, try to identify their existing use, and determine if there has been any adverse decisions against their mark. Moreover, an analysis of where the particular trademark falls along the distinctiveness continuum will likely dictate the next steps.
Third, you should try to identify whether any trademark defenses exist as it relates to your use. For example, you may be subject to the defense of fair use, which includes nominative fair use, and be able to avoid any claims of trademark infringement based on the same. Obviously, identifying a position without the benefit of a fair use defense necessarily requires an analysis of the trademark infringement factors. If you are simply going to rely upon the argument that there is no likelihood of consumer confusion, and thus no trademark infringement, you should be prepared to identify why the marks are different, how the goods and services are different, how the consumers are different, and related items as noted above.
Finally, you should consider what your goals are. If you are simply willing to rebrand, then you may wish to correspond with the trademark owner in hopes of getting the release of liability and amicable resolution. However, if your goal is to continue use of your mark, there may be ways to allow peaceful coexistence between the sender of the cease and desist letter, or alledged trademark owner, and yourself. This may be based upon a consent agreement or some other kind of agreement that limits use in a way, such as based upon geographic location, which would be memorialized in a concurrent use agreement. Regardless, understanding how the matter can be resolved without the need for either a trademark infringement lawsuit in federal court or even proceedings before a trademark trial and appeal board is extremely important.