Royal Mail is the national postal service of the United Kingdom, but there are several words and phrases that can be used as synonyms for this term. Some of the most commonly used synonyms include British postal service, UK postal service, and national mail service. Other potential synonyms for Royal Mail could include England's postal system, Scotland's postal system, or Wales' postal system, depending on the specific region being discussed. Other colorful expressions for Royal Mail might include "the mail man," "the postie," or "the letter carrier." Overall, there are many different ways to refer to the postal service in the UK beyond simply using the term "Royal Mail".