CFO may say you do not need an ATT to go to the PO, but they are incorrect. ATT is required for all transport of a restricted firearm, and if not covered under your 'long term ATT' a short tem is required.
Shipping through Canada Post -
Please contact the Canadian Firearms Centre at cfc-cafc.gc.ca or by calling 1-800-731-4000 to determine whether it is permissible to ship your firearms.
When it is determined permissible to ship firearms, they must be shipped as follows:
Customer Type Service To Be Used:
Consumer - Regular Parcel with Signature option.
Contract customer - Expedited Parcel with the Proof of Age (18 or 19) option using EST. Visit Section Mail addressed to children of Policies for an age of majority by province or territory listing.
Customers who wish to ship firearms must:
•unload the firearms - there cannot be any ammunition in the firearm or in the package (bullets, cartridges and other ammunition are dangerous goods)
•attach a secure locking device to the firearms
•lock the firearms in a sturdy, non-transparent container, and
•remove the bolt or bolt carrier from any automatic firearms (if removable).
Firearms cannot be shipped via air and cannot have any markings on the outside of the packaging. The customer is solely responsible for meeting all Canadian Firearms Centre regulations.
Personal or business have the same regulations for securing and packaging a firearm. Every customer using Canada Post MUST attach a secure locking device to the firearms and lock the firearms in a sturdy, non-transparent container
Some do, some don't, but the law is as posted.