For the mailman..rules on accepting gifts:
Gifts From Outside Sources
The following series of questions and answers addresses common inquiries regarding gifts from outside sources. All U.S. Postal Service® employees must adhere to these rules governing ethics.
Q. How do I know when I may not accept a gift?
A. With some exceptions mentioned later, you may not accept a gift from anyone who is giving the gift to you because of your government job. Ask yourself if the gift would have been offered if you were not working for the government. You are not permitted to solicit or ask for gifts under any circumstances.
You may not ask for or accept a gift from people or organizations that do business with, seek to do business with your agency, who seek some official action by your agency, or who have activities regulated by your agency. Gifts from these people or groups are prohibited whether or not you deal with them when doing your job. You must also decline a gift from someone who has interests that may be significantly affected by you when you are doing your job.
Q. What about accepting a cup of coffee?
A. A cup of coffee is acceptable. It is such modest refreshment that it is not considered a gift. So you may accept it without worrying about who is giving it or why. Other inexpensive food items such as doughnuts or soft drinks may also be accepted. There are some other items that are not considered gifts, such as greeting cards and bank loans at commercial rates. But remember that the definition of a gift is very broad. Generally, anything that has monetary value is considered a gift. If you have a question about a gift, ask your ethics official.
Q. May I accept a lunch?
A. It depends. Meals are gifts. If the person who wants to pay for your lunch is regulated by, does business with, or seeks official action by your agency, or is affected by the job you do, or if the meal is offered because of your position, you must decline the meal. However, you may be able to accept a lunch or other meal under an exception for gifts valued at $20 or less. Note that there is a $50 per year limit on gifts, including meals, from any one source.
Q. May I accept any other gift valued at $20 or less?
A. Yes, but no cash, in any amount, may be accepted. The $20 exception may be used to accept any gift that is not worth more than $20. A pocket calculator, for example, could cost from $5 to $100 or more. Just be certain that value of the gift is not greater than $20.
There are some other things you should keep in mind before you use the $20 exception. The rule allows you to accept gifts worth $20 or less on a single occasion. That means if several gifts are given at the same time, their total value cannot exceed $20. Again remember, there is a $50 per year limit on gifts from the same source.
There are other exceptions that would allow you to accept gifts that would otherwise be prohibited, such as the "friends and family" exception for gifts based on personal relationships. Other examples are special discounts available through your agency credit union and gifts that result from an outside job when they are not given because of your government position. All of the exceptions are subject to certain limits and some have conditions that must be met. Before using an exception, the best course to follow is to ask your ethics official about it.
Your ethics official can also tell you how you may properly dispose of a gift that you have received but are not allowed to keep.