Noun
post town (plural post towns)
(UK) A locality for the purpose of classifying postal mail by delivery area.
Post towns rarely correspond exactly to administrative boundaries and their associated physical features.
Laleham does share a post town, and has a large sports ground named after Laleham and Staines. Source: Internet
The "Manchester City Zone", " Manchester post town " and the " Manchester Congestion Charge " are all examples of this. Source: Internet
The rest of the Belfast post town is divided in a broadly clockwise system from BT3 in the north-east round to BT15, with BT16 and BT17 further out to the east and west respectively. Source: Internet