Question for USPS workers - Are mail carriers allowed to accept cash tips from customers?  Is it not allowed but still done?  Just wondering, I have always heard that people do it, not sure if it is expected.

Question for USPS workers - Are mail carriers allowed to accept cash tips from customers?? it is not allowed

Is it not allowed but still done??  yes- its done all the time. if you want to tip, but still follow the rules, small denomination gift cards (maybe 5 to 10 dollars) to fast food places or a coffee house IS within the rules. Snacks are good too, either store bought or homemade.

Just wondering, I have always heard that people do it, not sure if it is expected.  
Its not expected at all, but it is very nice to find an unexpected treat.

You may accept a gift from an outside source if:
the gift is based on a personal relationship? friend or family; or
the gift is valued at $20 or less (but aggregate sum of gifts, from that same source, cannot exceed $50, in a calendar year).

What if I am offered a gift of cash?
Postal employees absolutely CANNOT ACCEPT CASH or investment interests FROM OUTSIDE SOURCES.

Cash does not include retail gift cards with a face value of $20 or less that are designed for use in a specific retail store and cannot be converted directly to cash.

Any other day, my carrier crams mail into my mailbox - most of it usually actually mine - unless the package won't fit, then she just throws it on the ground by the mailbox. As often as not, she doesn't even check to see if there's any outgoing mail already in the box.

Lo and behold though, on December 24th this year, she knocks on the door with her cute little Santa hat on, and mail all neatly bundled together, delivered with a cheerful "Merry Christmas!" What? Expecting a tip for good service one day a year? I don't think so!

This year I gave my rural carrier a gift card to Subway for $15.00. She drives 78 miles a day on her route and has a CD player in her car. Last Christmas I gave her an audio book  which i got from my PBS trades. 

I have the best Mailman ever.  He does a rural route by car.  He is always on time.  We have talked about PBS and he picks up my outgoing stamped PBS packages from my mailbox.  Saves me lots of time and money.  I gave him a tip this and he left me a very nice Thank You post card.  I felt the tip was well deserved.  It really makes a difference if all goes well with your mail.  Sometimes if I'm getting too many PBS packages to put in the mailbox, he will stash them in an agreed upon spot for me.