A Complete Guide to USPS Mailing Services and Packaging Necessities in 2025

Understanding the core USPS domestic shipping services

To ship successfully with the USPS, you must first speak its language. This starts from the very basic understanding of their tiered system domestic services. These services include shipping solutions based on the product packaging boxes size, weight, and high-speed delivery options. However, knowing which service fits your needs and wallet can be a challenge. Because choosing the right service shapes your shipping budget to your customer satisfaction rating. So, let’s explore these services in detail.

First-Class Mail (Letters & Flats)

First-class mail is a service for shipping bills, invoices, postcards, letters, and large envelopes. Thus, it is the most cost-effective shipping service for lightweight items. Whether you mail a letter across the street or across the country through first-class service. It won’t affect the cost. It’s the weight brackets that determine the pricing tier. For instance, the cost of a mail that weighs up to one ounce is $0.64and or 2 ounces its $0.88. Thus, the heavier the mail, the more expensive it gets. However, there is a weight restriction. You cannot ship a letter or flat that is more than 13 ounces. For mails above 15 ounces there is a ground advantage service.
First-class mail is a fast shipping service. Its delivery period is within 1 to 5 business days. Moreover, it offers free forwarding and return services. But, it doesn’t provide the tracking facility. You can choose first-class service for both domestic and international mail.

Priority Mail

Priority mail is a go-to option for shipping letters, flats, and parcels that weigh between 13 ounces to 70 lbs. The defining feature of this service is the speed. The recipient can receive the mail within 1 to 3 business days. Whereas in priority mail the cost is calculated by the weight and the distance the package travels. The biggest advantage of the priority mail is the package insurance. You get $100 insurance with a tracking facility.

Priority Mail Express

Priority mail and priority mail express services have the same shipping standards. Such as the weight limit is 70 lbs., delivery period is 1 to 3 business days, $100 insurance and tracking is included. Priority mail express service stands out due to its included advantages. Like priority mail doesn’t guarantee a delivery within 3 business days. It’s just an estimated time period. Whereas express mail is 100% guaranteed service. Moreover, it is a year-round service, available 365 days a year. That’s why it is a little costly.

USPS Ground Advantage (The New Standard)

If your parcel weighs more than 13 ounces and you want the lowest shipping charges. Then, ground advantage is the ideal service. USPS introduced this service in 2023. Ground advantage offers quick delivery in 2 to 5 business days (estimated) with tracking facility, and $100 insurance. This service is unique for its handling of hazardous goods. Such as perfumes, aerosols, and lithium batteries.

Essential USPS packaging standards

There is one common mistake that many people make while packing their parcel. It’s the inappropriate packaging. Every year, millions of mails and parcels are damaged, delayed, and sometimes are refused by the postal service because they are not up to the packaging standards. Following is a list of USPS mailing services packaging rules. Packing your product according to these guidelines can help you prevent costly re-shipment. Plus there aren’t any suggestions. These guidelines are mandatory for USPS compliance and error-free delivery.

Dimensions and Weight Limits for Compliance

According to USPS poly mailer rules, the length + girth measurement of the package must not exceed 108″.
The maximum weight limit is 70 lbs.
Use a round up figure for the package weight to avoid under payment.

Selecting the Right Container

It is advised to use corrugated cardboard, Kraft packaging boxes, or postage mailing bags for packaging the content. As these containers are durable and can withstand rough handling during transit.
Old food boxes are unacceptable as they are flimsy and lack the necessary strength.

Cushioning and Internal Protection

If the shipping container has empty space or voids. Or the shipping content is fragile like perfume bottles. Use additional materials as bubble wraps, foam, or packing peanuts as a second layer of protection.

The Right Way to Seal a Package

Package sealing is very important as it often leads to accidental opening and damage. Therefore, use a 2-inch packing tape.
Refrain from masking or duct tape because their adhesion quality is poor. Thus, making the seal easy to open.
While applying tape on the parcel, use the H-taping method. This means seal all three seams on both the top and bottom in the shape of an “H”.

Addressing and Labeling Standards

There is a specific format for writing the address. It should be clear, concise, and the letter should be in uppercase format with no punctuation.
Affix the shipping label to the package’s longest dimension.
Use the full ZIP+4 code.

List of USPS Prohibited Items

There are some items that are completely off the limits of USPS mailing services. No matter what the circumstances are. Or whether they are used for a positive purpose. USPS doesn’t ship these items under any condition. These items are:

Airbags
Counterfeit or pirated goods
Gasoline
Marijuana
Ammunition
Hazardous waste

Where to get USPS packing materials

USPS packaging materials include shipping boxes, envelops, flats, mailers. These packaging containers are easily available on the USPS website. You can order online or even get them from your nearby local post office at free of cost. However if you want customized USPS containers you can get it from Boxit Packages. We manufacture USPS-friendly corrugated and Kraft boxes with personalized designs. You can get additional shipping materials for product safety. Contact our customer representative for more information.