The Hobbits of the Shire - at least those who could read and write² - delighted in sending letters to one another. The Shire provided for this with an extensive Messenger Service, in which numerous Messengers or postmen carried letters to and from post offices scattered throughout the Shire, even in villages as small as Bywater. Like the smaller Watch, this service was attached to the office of the Mayor of the Shire, so that one of the official titles of the Mayor was 'Postmaster'.

The role of Postmaster seems to have carried little actual responsibility, as the Mayor was said to have had few real official duties of any kind. Nonetheless, there were times when urgent action was needed: for example, the invitations to Bilbo Baggins' Birthday Party of Shire-year 1401 overwhelmed the Messengers, so that volunteer postmen had to be organised. Presumably it was the Postmaster who did this organising, though it's unclear what specific role the Postmaster (at that time Mayor Will Whitfoot) played in this minor postal emergency.

The position of Postmaster was an office of the Mayor of the Shire. For a list of known Mayors (and therefore also Postmasters) see the entry for Mayor of Michel Delving.