The information provided with a trademark application to the U.S Patent and Trademark Office (USPTO) is public record. There are a large number of unscrupulous organizations that take this data and mail invoices for worthless services or send documents that mimic the look and feel of official government documents.
You can safely ignore any paper letter you receive that includes official government data like the USPTO application serial number, the registration number, the International Class(es), filing dates, and other information that is publicly available from USPTO trademark application records.
Typically, these scams present offers related to (1) international trademark registration; (2) trademark monitoring services; (3) to record trademarks with U.S. Customs and Border Protection; and (4) to "register" trademarks in the company's own private registry.
These companies may use names that resemble the USPTO name, including, for example, one or more of the terms "United States," "U.S.," "Trademark," "Patent," "Registration," "Office," or "Agency." Many refer to other government agencies and sections of the U.S. Code. Most require "fees" to be paid.
Trademark Registration and Monitoring Office (Intellectual Property Rights Recordation Alert) (Los Angeles, CA)
United States Trademark Registration Office (Los Angeles, CA)
Trademark Renewal Service (Washington, DC)
Trademark Renewal Service (New York, NY)
Intellectual Property Services USA Incorporated (Alexandria, VA)
Intellectual Property Agency Ltd. (London, U.K.)
Registration of International Trademark WDTP (Praha, Czech Republic)
WIPT World Patents Trademarks (Bratislava, Slovak Republic)
United States Trademark Maintenance Service (version 1) (Arizona)
United States Trademark Maintenance Service (version 2) (Arizona)
U.S. Trademark Compliance Service (Phoenix, AZ)
IPTO International Patent & Trademark Organization (Brno, Czech Republic)
TM Collection (Szombathely, Hungary)
Patent Trademark Register
Register of International Patents and Trademarks (Bratislava, Slovak Republic)
Trademark Safeguard - Trademark Monitoring Service (New York, NY)
USTM Information Services (Idaho Falls, ID)
Brand Registration Office (Trademark Selection Edition) (Washington, DC)
TM Edition (2012 version) (Szentendre, Hungary)
TM Edition (2015 version) (Szentendre, Hungary)
TM-DB Register of Protected Trademarks (Washington, DC)
TM-DB Register of Protected Trademarks (Wilmington, DE)
TM-DB Register of Protected Trademarks (Pearland, TX)
IOPR - Intellectual Office Property Register (Beaverton, OR)
GBO, Inc., Trademark and Patent Dep. (Miami, FL)
IPTI - International Patent & Trademark Index (Czech Republic)
RPT Servis - Registration of the International Trademark (Czech Republic)
TPP - Trademark & Patent Publications (Poland)