In principle the mail system in Senseless works the same way, but using the general cargo bay and drop-off stations. I would like to include dedicated mail assets, but my 3D and graphics talents are non-existent. I would not know how to model these assets. But If they were available and free to use, then I certainly would include them.

Addition:

actually some residential buildings produce mail by random, some demand it and many do not do the one or the other.
(Some produce waste).

To get the mail collected I have to place a cargo truck hub inside the residential area.
And the footprint of the cargo truck hub is huge, regarding the small use of collecting a few letters.

That thing is way too big - I prefer the way the Post Mod handled that.

The post office buildings had small footprints and could be placed between buildings with only one or max. two buildings to be demolished.
They produced UNSORTED_MAIL depending the amount of residential buildings inside their area.

I totally agree about the size of the cargo bay for collecting mail. I'm going to see what I can come up with.

The introduction of UNSORTED_MAIL could indeed be interesting, now I think about it. Good suggestion!

Mail is indeed randomly spread though the town, so that the amount of mail is relatively in the same order of magnitude to the amount of commercial goods and industrial goods. I like this approach of randomness. It brings some organic, chaotic feel and less all the same.

Thank you for the update, I will see how it goes with UNSORTED_MAIL.