I constantly have clients calling me in a panic saying that they received a bill from (insert a company name) and that they don't know whether or not to pay it or what it is.
Here is the answer: If you have used me to file your Trademark application, that means that I am the attorney of record. As the attorney of record, any correspondence from the patent and trademark office will come to me. So unless I am calling you and letting you know that something has happened on your case, the mail that you are receiving is not from the trademark office. Thus, you do not have to pay any fees in order to maintain your Trademark rights. Another way to confirm that the documents are likely junk is to check the physical location of the return address. Unless it is Alexandria, Virginia, where the patent and trademark office has a physical office, it is likely junk.
So why are they sending you this? To get your money. They are hoping that you don't understand what the mail is and think it is actually from the patent and trademark office. Thus, hoping you will just pay for it. They also may be trying to convince you that they can provide a particular service for you. A common service is patrolling the Official Gazette, which the Trademark office publishes every Tuesday. Before any Trademark can be federally registered, it has to run in the Official Gazette for 30 days. During that time, an opposing party may file a Notice of Opposition to try to stop your Trademark from registering. Thus, these companies may be offering to patrol the Official Gazette in order to catch someone who may be infringing upon your mark. Here is why, in my opinion, you do not need to pay someone to do this for you: