During the second she transported EIC troops to Macao to augment the Portuguese forces there, but the authorities there refused them permission to land.

In 1814 Dover Castle was sold and she served for a half-dozen years as a London-based transport.

[2] Macao Expedition: During the French revolutionary and Napoleonic Wars the British Government and the EIC feared that the French would capture one or more of Portugal's colonies of Goa, Damam, Diu, or Macao and use it as a base for operations against Britain's possessions.

In 1801 the Admiralty asked Admiral Peter Rainier, the commander-in-chief of Royal Navy operations on the East Indies Station to assist the Portuguese at Macao.

It stopped at Penang to exchange the Marine Battalion for soldiers there and at Malacca who would be better suited to the task at hand.

Lieutenant-Colonel Hamilton then had the expedition stop at Amboina to take on water so that there would be sufficient on hand if the troops could not land at Macao.

[2][4] The Governor of Macao refused on 24 March to give permission for the troops to land, absent orders from his superiors at Goa.

Dover Castle reached St Helena on 6 August, and arrived at Diamond Harbour on 28 November.

[2] Captain Richardson sailed from Portsmouth on 18 June 1806, bound for St Helena, Madras and Bengal.

[2] Lloyd's List reported that the Indiaman Dover Castle had retaken Admiral Rainier, country-ship, at 3°N 89°E / 3°N 89°E / 3; 89, on 30 December 1806.

[7] The officers and men of the Indiamen Lord Keith and Dover Castle received salvage money in October 1810 for the recapture of Admiral Rainier on 31 December 1806,[8] as did Ocean.

Homeward bound, she was at Diamond Harbour on 18 June, Saugor on 9 August, and Vizagapatam on 12 September.