What is another word for first-class mail?
Pronunciation: [fˈɜːstklˈas mˈe͡ɪl] (IPA) 
First-class mail refers to a type of postal service that delivers letters, cards, and other correspondence quickly and efficiently. However, there are several synonyms for this term that can be used interchangeably. These include Priority Mail, Express Mail, and Expedited Mail. Priority Mail typically offers faster delivery times than first-class mail, while Express Mail guarantees overnight delivery. Expedited Mail may also be used to indicate fast and efficient mail delivery. Other synonyms for first-class mail include Certified Mail, Registered Mail, and Return Receipt Requested, which are all specialized mailing services that offer additional tracking and security features.
