Postal Service, available in 
Empire of the Skies DLC, is a system which is based on transporting mail between islands and regions in order to connect the population across the world. It adds lifestyle needs for different types of mail for most of the population tiers, which provide more residents and income, while not increasing consumption rates of other needs. Mail is generated by Post Offices and Post Boxes placed within residential districts. It can be distributed among the population on the same island as Local Mail or transported to other islands via airship routes as Regional or Overseas Mail.
Mail types[]
There are three main types of mail and communication lifestyle needs that correspond to them:
Local Mail – this type of mail is the one that is produced by post offices and post boxes. It can be provided to population on the same island or can be transported via airship routes to other islands to provide them with Regional or Overseas mail.
Regional Mail – it cannot be directly produced. It is obtained by using airship routes to transport mail between islands of the same regions. It cannot be loaded on airships and transported, it has to be consumed on the island it arrived to.
Overseas Mail – it cannot be directly produced. It is obtained by using airship routes to transport mail between islands of different regions. It cannot be loaded on airships and transported, it has to be consumed on the island it arrived to.
The combination of Empire of the Skies and 
Land of Lions DLCs adds another type of mail: 
New World Reports. It can be generated via an item New World Science Reporter equipped in a 
Town Hall that affects an operational post office or a post box in the New World. Additionally, the combination of Empire of the Skies, Land of Lions and 
The Passage DLCs adds 
Arctic Reports. They are generated in a similar way, with an item Arctic Science Reporter equipped in an 
Arctic Lodge that affects a post office in The Arctic. Both of those special types of mail can be provided to 
Scholars as lifestyle needs in order to increase the scholar population and their research points generation per minute.
Producing and storing mail[]
Mail is produced by post offices and post boxes that function similarly to production buildings, but their productivity is based on amount of residents in their radius: 500 population corresponds to 100% productivity. The more people within the radius, the higher the productivity, up to 3100% at 15500 residents. The radiuses of post offices and post boxes cannot overlap so every residence can contribute to mail production at only one building.
The only main type of mail that gets produced in this way is the Local Mail. Additionally, New World Reports and Arctic Reports can be produced – in form of extra goods when appropriate items are in use. Regional and overseas mail cannot be produced, they have to be created from local mail that is transported between different islands.
Mail has a separate storage capacity, not tied to the trading post or depots in the harbour area. Storage capacity for all types of mail is increased by airmail sorting offices, post offices and post boxes. Constructing one of those buildings is the only way of increasing it. Just like in case of other goods, all mail that is in storage is automatically available across the entire island, people can consume it as long as appropriate needs are unlocked and active.
Transporting mail[]
In order to provide the population with other types of mail than only Local Mail, the mail has to be transported between islands via airship routes. Unlike other goods, mail cannot be manually loaded or unloaded, it also cannot be used for trade. To be a part of an airship route, an island requires an Airship Platform and an Airmail Sorting Office. Airships on airship routes can load/unload mail only at airship platforms.
When setting up an airship route and choosing goods to load, only Local Mail, New World Reports or Arctic Reports can be selected. The amount of mail to load can be changed but the amount to unload is always 50 tons and cannot be changed. All mail loaded at one island is automatically unloaded at the next destination. If the storage of the destination island is full, the excess simply disappears and gets wasted. When the destination island is within the same region/climate, the Local Mail is transformed into Regional Mail and the destination island receives Regional Mail in the same amount as the amount of Local Mail that was loaded. In case of the destination island being in a different region/climate, all Local Mail is transformed into Overseas Mail. Old World and Cape Trelawney are considered as the same region/climate, and mail transported between them transforms into Regional Mail.