The Post Office Packet Service dates to Tudor times and ran until 1823, when the Admiralty assumed control of the service. Originally, the Post Office used packet ships to carry mail packets to and from British embassies, colonies and outposts. The vessels generally also carried bullion, private goods and passengers. The ships were usually lightly armed and relied on speed for their security. However, Britain was at war almost continuously during the 18th and early 19th centuries with the result that packet ships did get involved in naval engagements with enemy warships and privateers, and were occasionally captured.

Packet boats, offering a regular scheduled mail service, had been in use for the sea route between Holyhead and Dublin since at least 1598, providing a mail connection between Britain and Ireland. Furthermore, during Essex's campaign, additional packets were run out of Falmouth and Milford Haven, sailing to and from Waterford on the south coast of Ireland; but these services were relatively short-lived (albeit the Milford-Waterford route would be revived during the Commonwealth period in the 1650s).

For letters to and from continental Europe, a different approach was taken: the post was entrusted to messengers, who would then make their own arrangements for conveying it across the Channel and beyond. This messenger service was far from reliable, so in the 1630s Thomas Witherings set about establishing a regular Dover-Calais packet service and entered into negotiations with Flemish and French postmasters-general to negotiate for effective cross-border carriage of letters for mutual benefit of the nations concerned (and the messengers were promptly dismissed).

To begin with, letters to and from Holland went via France; but in 1668 a regular packet service was set up in addition to run between Harwich and Helvoetsluys. By the 1680s packets were running to Ostend or Nieuport from Dover, as well as to Calais. The route to France, however, was then closed in 1689 following the start of the Nine Years' War.

In 1690 the packet service consisted of eleven vessels: three for the service to and from Ireland, two for Holland, two for Flanders and two for France (albeit the latter service was suspended). The other two packet boats worked out of Deal, and provided a mail service for warships and merchant vessels anchored in the Downs. In place of the Dover-Calais route, a packet service was established between Falmouth and Corunna in north-west Spain.

At the outbreak of the War of the Spanish Succession, in 1702, the service to France was again closed and the Iberian route was diverted to Lisbon. Also at this time, Edmund Dummer undertook to run a monthly packet service between Falmouth and the West Indies; problems arose, however (leaving Dummer bankrupt) and a West Indies service was not resumed until the 1740s.

In 1744 there were four boats on the Falmouth station, four at Harwich, six at Dover, two based at Gibraltar and two at Minorca (while additional vessels, at various stations, provided packet services with Ireland, the Downs and several island communities). The following year additional vessels were procured for the resumption of the service between Falmouth and the West Indies, and before long packet ships were sailing from Falmouth to Buenos Ayres, Colombia, Cuba, Mexico and San Domingo.

Routes ran at various times from Dover in Kent and Harwich in Essex to Calais, the Hook of Holland, Heligoland and Gothenburg.