Hi, you can achieve most of this today with existing mods, though I don't know if there are any for making smaller catchment areas.

This mod adds mail as a cargo to/from the town buildings, plus a mailing sorting centre to take it to/from:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1962151270

You can then use any vanilla or mod vehicles and stops/stations that you like to pick up and drop off the mail. I suppose you could also place asset mailboxes for looks.

Cheers

don't mean to offend or be rude dude but i am an experienced player as someone who has played from the day of release.

i do know what mods are out there, and have used that mod

i am looking for

1 a more realistic feel to my cities
2 to use how it should be.

Ah. Well then hopefully someone makes a mod like this for you someday.

Sadly the reality is that 99.9% of mod requests never happen (unless you actually hire a modder, which is an option), so hopefully the info I shared helps others here know what's available today that they could use instead.

Cheers