Aden

The "Michel, Asien II 1989/90 Übersee-Katalog - Band 5/II", 1989 lists the following 3 areas of Arabia as Aden.
The descriptions come from Linn's "Stamp Issuing Entities Of The World" page.

Hadhramaut, Kathiri State in (1967)
Stamp-issuing status: inactive. A region in southwestern Arabia, formerly part of the Aden Protectorate. A number of large, colorful pictorial sets and souvenir sheets were released to the collector market in the months preceding the territory's absorption by the People's Democratic Republic of Southern Yemen.

Mahra (1967)
Stamp-issuing status: inactive. A sultanate in the Aden Protectorate in southwest Arabia. Mahra briefly issued stamps before its absorption into the People's Republic of Southern Yemen

Seiyun, Kathiri State of (1942-67)
Stamp-issuing status: inactive. A former British protectorate in south Arabia. The area was autonomous until its incorporation into the People's Republic of Southern Yemen.