You can ship a UPS package in a USPS box. While it may seem unconventional, there is no specific rule or restriction that prevents you from using a USPS Priority Mail box for shipping with UPS. UPS will accept packages regardless of the type of box used, as long as it meets their size and weight requirements.
However, it is important to note that using a USPS box for UPS shipping may cause some confusion or potential issues during the shipping process. This is because the USPS box is specifically designed for USPS services, and using it for UPS shipping may lead to misidentification or mishandling of the package.
To avoid any potential confusion, it is recommended to take some precautions. One option is to fold the USPS box inside out, so that the USPS logos and markings are not visible. This way, the package will appear like any other generic box, reducing the chances of confusion during transit.
Additionally, you can also consider covering any USPS markings or labels with blank adhesive labels or tape. This will further obscure the USPS branding and make it less noticeable.
While these precautions can help minimize confusion, it is worth mentioning that there is still a possibility that the package might be identified as a USPS box during the shipping process. If this happens, it is unlikely to cause any major issues, as both UPS and USPS are reputable shipping carriers and have well-established processes for handling packages.
While it is technically possible to use a USPS Priority Mail box for shipping with UPS, it is recommended to take precautions to minimize any potential confusion. Folding the box inside out or covering USPS markings can help make the package appear more generic, reducing the chances of mishandling or misidentification during transit.