A pennant system for signalling the mails was approved by the Resident in May 1866 and used experimentally from November that year, pending approval from the Postmaster General in Bombay, which was forthcoming in January 1867.

The harbourmaster was responsible for announcing the sighting of a mail Packet as it approached Aden harbour and when the service to the Cape via Zanzibar was introduced in December 1872 he issued a notice that the signal to be hoisted at the various signal stations would be the letter F in the commercial code (a white ball on a red pennant) together with the usual time signal indicating at what time the Zanzibar mail would close. He helpfully added that a booklet on signal codes could be bought from his office for six Annas each.

Only three days later the code letter was changed to the letter G, a yellow and blue flag. The nautically-minded reader will have realised that these code letters were different from those in the 1931 International Code of Signals, Visual, in use today. The first International (Commercial) Code of Signals was introduced in 1857, being updated on 1st January 1901. The 1857 Code consisted of only 18 flags, compared to 26 in 1901 and the 40 in the 1931 Code which came into effect on 1st January 1934.

At night signal guns were fired to announce the sighting of the more important mail packets. In some instances coloured lights were also shown. A Notice advised the community that from 1st December 1879 the following signals would be made at night:

For the P & O mail to and from Bombay: At the lightship 3 guns in quick succession, repeated at Marshag and Sham Shum by 2 guns in quick succession.

For the Messageries Maritimes mail to and from Suez: At the lightship 2 guns, repeated by one gun at Marshag and Sham Shum.

The P & O mail steamer to and from Calcutta would be signalled as before viz: At the lightship one gun would be fired and one blue and one white light shown at the ensign staff. This signal was not to be repeated at any of the other stations.

Two of the most important routine events of the week at Aden were the arrival of the weekly P&O mail steamers, one from Bombay and the other from Europe via Suez. Once Perim had been connected to Aden by cable, and bearing in mind that it then took the packet another six hours to reach Aden, it meant that advance warning could be given of the estimated time of arrival at Aden of the mail steamer for Bombay.