The answer to this question is sometimes. If you ask an everyday mailman doing a postage run if you can buy a stamp off them then the answer is no, you cannot buy a stamp from the mailman. However it is possible to have him deliver some to you. If you go to usps.com and create an account your mailman can deliver you stamps directly to your door. If you live in a rural area without easy access to a USPS outlet than the mailman does a number of other extra services including selling postage stamps. On top of that they can also process your mail for you whether it be Standard Mail, Express Mail, or Priority Mail.