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The information in this publication is primarily for companies and customers who mail parcels and special items. For parcels to be accepted for mailing, they must be prepared according to the requirements and guidelines in this publication. More detailed packaging and mailability requirements are in module C of the Domestic Mail Manual (DMM) and in the International Mail Manual (IMM). Requirements specific to each class of mail are covered in those manuals.
State and federal regulations also can affect the mailability of parcels containing certain items such as hazardous, biological, and restricted materials. The Postal Service accepts properly prepared and marked parcels, but it reserves the right to refuse parcels that contain nonmailable items or that seem improperly prepared.
Items sent through the mail must be packed in a way that prevents their deterioration or degradation. Large-volume mailers should test before shipping to determine their packaging's effectiveness and the product's durability.
Mailers can use the International Safe Transit Association (ISTA) Test Procedure 1A to evaluate their packaging (see Appendix A). Mailers can also contact the nearest postmaster, account representative, or business mail entry manager for a review of their packaging.
In the transportation industry, the term load is defined as a quantity of material assembled and packed as a shipping unit. Generally, packages are classified into three load types based on the nature of the contents, how well the packaging protects it, and the strength of the mailing container.
Easy loads include moderate-density items that can completely fill the mailing container or be packed in interior receptacles. Easy loads are not readily damaged by shock, compression, or puncture during handling or mail processing. They do not shift or move within the container, and they usually do not endanger other parcels.
Average loads include moderately concentrated items that usually provide partial support to all surfaces of the mailing container. Often, the item can be damaged if the package is compressed.
Average loads can be placed directly into a container or into separate interior containers. Nesting items within partitions or separate paperboard boxes can stabilize an average load and prevent damage to the container and the items.
The items in difficult loads usually need additional protection against shock, puncture, or distortion during handling or mail processing. Fragile objects, delicate instruments, high-density items, and small bulk items are considered difficult loads. Paper boxes, paper or plastic bags, or wraps of any kind cannot support difficult loads and are not acceptable containers for such items.
Besides load type, packaging acceptability is one of the principal standards of mailability. A container must not be packed in a way that might cause or allow its contents to injure Postal Service employees or to damage other mail or mail processing equipment. Fragile items must be packed to withstand mail processing and transportation. Heavy items must be braced and cushioned to prevent damage to other mail.
Items described in 1-4.2 through 1-4.5 often cause problems when improperly packaged. Requests for exceptions to the requirements in this section must be made to a rates and classification service center (RCSC) (see Appendix B for addresses).
Stationery items often become loose during mail processing. Problems are caused by unrestrained, concentrated, or shifting contents and by inadequate internal packaging, containers, closures, and reinforcements.
Stationery items that are thicker than 1 inch or heavier than 1 pound may not be mailed in letter-style envelopes. These items must be unitized by tying or banding them or by partitioning tight containers to prevent shifting.
Liquids can damage or destroy other mail and mail processing equipment. Generally, containers of liquid with only friction-top closures (push-down type) are not acceptable. Screw-on caps, soldered tops, clips, or other means are necessary for secure closing.
Glass and other breakable containers holding more than 4 fluid ounces must be cushioned with a material that can readily absorb any leakage. These primary containers must be placed and packed inside sealed, leak-proof containers. If a container holds more than 32 fluid ounces, it is not acceptable for mailing unless cushioned as described above and packed within another sealed, leak-proof container such as a can or plastic bag. The outer mailing container must be strong enough to protect the contents, must be marked "LIQUID," and should display orientation markings (i.e., up arrows) that indicate the upright position of the parcel.
Steel pails and drums with carrying handles and positive closures (such as locking rings or recessed spouts under screw-cap tops) are acceptable for mailing without additional packing. Requests for exceptions to these requirements must be made to the nearest RCSC (see Appendix B for addresses).
Aerosol containers with inadequate friction-cap closures or other nonpositive means to prevent accidental discharge of contents can injure Postal Service employees or damage other mail and mail processing equipment. These containers must be constructed to prevent accidental discharge of their contents in the mail.
Recessed valves, screw-thread caps, tape closures, or other secure closures can make such containers acceptable.
High-density loads (such as tools and machine parts) can be dangerous to Postal Service employees and to other mail and mail processing equipment. High-density loads that weigh between 15 and 35 pounds are machinable on Postal Service mail processing equipment if the loads are packaged so that they do not exert more than 60 pounds of pressure per square foot (0.4167 pound per square inch) on the smallest side of the mailing container.
Packaging that does not meet the minimum requirements in this publication may be permitted under a "test" status. The manager at the originating bulk mail center (BMC) is authorized to approve this test status. Contact the local postmaster for the address of the nearest BMC.
If the BMC manager approves the test packaging and the packaging achieves acceptable performance levels, the mailer may continue using the packaging. If the BMC manager disapproves test status, the mailer may appeal this decision with an RCSC (see Appendix B for addresses).
If a mailer asks to use packaging that deviates significantly from postal requirements, the manager of Mail Preparation and Standards at Postal Service Headquarters must be notified. If the deviation cannot be resolved by the accepting postmaster, the BMC manager, or the business mail entry manager, the mailer's request is referred to the rates and classification service center.
Mailers should take appropriate precautions when packaging a parcel of mailable items that have the potential to injure any person handling or opening the parcel. Because a small child might gain unauthorized access to a parcel, every potentially harmful item should be enclosed in a container that is hard for a child to open.
If a mailer is unsure about whether an item is mailable or its packaging is acceptable, the mailer should send a written request to the nearest business mail entry unit (see DMM G042 for addresses). To ask for an exception to Postal Service packaging requirements, the mailer should submit a written request to an RCSC (see Appendix B for addresses). The request should fully describe the item and its packaging.
Postal regulations change from time to time. If there is conflicting information between this publication and the DMM or IMM, then the DMM or IMM takes precedence. Mailers may review copies of these documents at any post office, business mail entry unit, or postal business center. Both documents are available to the public through a subscription service handled by the U.S. Government Printing Office, and current versions are accessible on the Postal Service's "Postal Explorer" web page at http://pe.usps.gov.