1. Mail that includes letters and postcards and packages sealed against inspection
   - first class, 1st class, first-class mail

Type of: mail

• sorrower
• sorrowful
• sorrowfully
• sorrowfulness
• sorrowing
• sorry
• sort
• sort of
• sort out
• sort program
• sortable
• sorted
• sorter
• sortie
• sortilege
• sorting
• sorting algorithm
• sorting program
• sortition
• sorus
• SOS
• sostenuto
• sot
• soteriological
• Corinthian order