Along the same lines, the USPS code specifically states that Postmasters do not have the authority to over rule these regulations. So when someone at the PO says it is okay you can still go to jail. I have already come across Postal employees who will tell you no problem they don't care.
Well they don't care. It is you who will pay the price if caught. Several very high profile C&R websites routinely USPS handguns illegally and have told me they have been doing so for years with the blessing of the local Postmaster. I know of LGS who recommend customers mail their handguns. Ignorance is bliss till you are doing laundry for some thug in the slammer.
Len's course should be required for everyone. If you want to avoid jail in this state over firearms, don't believe what the guys at the range preach, don 't believe what the LGS teach, and don't listen to the vast majority of attorneys as there are very few attorneys in Massachusetts who practice in this area enough to understand the bowl of noodles approach to guns laws we have. Fortunately many of the expert attorneys are mentioned here in NES frequently.
Take Len's course. It doesn't only cover the law but will give you clear perspective of its origins and application. The big takeaway is in Massachusetts what law enforcement and prosecutors want will be delivered by the courts most of the time if they have to invent law or ignore it to cover.