IMBs are special barcodes used by the postal service on mail. They contain detailed information about each piece of mail, which helps USPS sort and deliver it efficiently. Marketers using these barcodes get discounts for automating their mailings. The IMB system isn't just about making mailing easier and cheaper—it also includes services like mail tracking.

The IMB has 65 vertical bars that store 31 pieces of data about the destination, mail options, applicable discounts, and other details. The first 20 digits of the IMB form the tracking code, which is divided into four parts along with a routing code, which we will learn about in-depth below.

What data does an IMB store? It is crucial to know about the bits of information an IMB contains so that it is possible to read an IMB or decode the data it contains. The 65 vertical bars of the IMB store 31 pieces of data related to the destination, mail option, discounts applicable, and more such details. The IMB barcodes help communicate these details to the sorting machines so that further operations can be carried out.

The Intelligent Mail Barcodes are made up of two sections – the tracking and routing code. The former section consists of information about the mailer and the unique mailpiece, wherein the latter consists of the destination ZIP code. The barcodes are made up of 20 to 31 digits of the data payload.

The first 20 digits of an IMB comprise the tracking code, which is further divided into four parts and a routing code:

Barcode Identifier (BI)

The BI is an essential part of the IMB and always consists of two digits. It is assigned by the USPS and is used for encoding the presort identification, usually printed on the Optional Endorsement Line (OEL) in a human-readable format. The BI is also used for the USPS’s future use. Previously, OneCodeACS and OneCodeCONFIRM users were asked to enter ‘00’ as the 2-digit BI. The USPS would later fill in the required digits. Technically, the BI is always zero except when used for flat-size mail pieces eligible for automation prices that bear the Optional Endorsement Line. In this case, the BI should correspond to the printed OEL.

The second digit of the BI should be within the range of 0-4. 00–04, 10–14, 20–24, 30–34, 40–44, 50–54, 60–64, 70–74, 80–84, and 90–94 are the approvable encoding ranges that all mailers have to follow carefully.

Service Type Identifier (STID)

The STID is three digits and represents the mail class and any additional service or a combination of services that the mailer has requested. Defining a mail item as either Full Service or Basic (also referred to as Non-Automation) is one of these services. Moreover, the STIDs are used to state how the sender wants the USPS workers to treat “undeliverable as addressed” (UAA) mail. The STID can also determine the form of address verification and correction that the sender has requested if any.

Some examples of basic STIDs that can be used only for automation purposes are:

040 – First-class mail, basic with destination IMB tracing
042 – Standard mail, basic with destination IMB tracing
044 – Periodicals, manual address correction
261 – Standard mail, no services
300 – First-class mail, no services
401 – Bound printed matter, no services
708 – Business reply mail, no services
710 – Priority mail, no services
712 – Priority mail flat rate, no services

Mailer ID

A mailer identifier is either 6 or 9 digits and is assigned by the USPS to identify mailers (the company sending out the mail items). Oftentimes, the mailer ID is also called the customer ID. High-volume mailers receive 6-digit mailer IDs, whereas low-volume mailers are given 9-digit mailer IDs. In order to distinguish between the 6-digit and 9-digit mailer IDs, you should know that every 6-digit mailer ID begins with a digit within the range of 0-8, and every 9-digit ID starts with the digit 9.

The Mailer ID is required to appear on all US mail barcodes, except for Origin IMB tracing barcodes wherein the mailer ID fields are combined with the serial numbers. The mailer ID remains the same for all mail items sent by the same mailer.

Sequence Number

The sequence number also referred to as the serial number, is unique for every mail piece and can be used to identify specific recipients. It can be assigned either by the USPS or the mailer themselves. Mailers also have the option to use the same sequence number for the entire mailing rather than individual mail pieces. If a Full-Service discount is claimed, these numbers should be kept unique for at least 45 days from mailing.

Mailers must ensure that the sequence number is either 6 or 9 digits long, depending on the length of the mailer ID. If only six digits were used in the mailer ID, there should be nine digits in the sequence number and vice versa. The mailer ID and the sequence number should contain a total of 15 digits altogether. Every USPS Intelligent Mail Barcode must have a sequence number, except when the mailer has opted for Origin IMB tracing. The mailer can always add zeros to fill up fields if required, and as per the USPS guidelines.

The routing code section of the post office IMB barcodes can be omitted and have zero digits. However, if it is added to the IMB, there is only one part to it called the Delivery Point ZIP code.

Delivery Point ZIP Code

It could contain either zero, five, nine, or eleven digits. Basically, the number of digits is decided by the different forms of writing ZIP codes. Many mailers stick with 5-digit ZIP codes, whereas some of them use ZIP+4 codes, which are always better to ensure deliverability. The additional two digits representing the delivery point are sometimes added to the ZIP codes. Hence, the length of this section can differ. The routing code was encoded the same way in the previously used POSTNET barcodes.

Let us have a tabulated look at all the IMB components:

The complete IMB digit string would look like 7270897823174253689710461

These numbers are then converted into barcodes using the IMB symbology.

 Also Read: How Long Will Mail Take From Zip Code To Zip Code?

The encoded IMB barcodes use the 4-state barcode symbology. It is called the 4-state symbology because four distinct symbols are used. Moreover, IMBs are also referred to as the 4-State Customer Barcodes or 4CB due to this reason. The four kinds of symbols are the full bar, ascender, descender, and tracker, which helps build the 65 vertical bars of the US mail barcode. Every bar has a tracker. Ascenders and descenders are ‘half’ bars that ascend and descend from the tracker, respectively. A full bar is a combination of all of the other three symbols. Refer to the image below for a better understanding.

The letters T(tracker), F(full bar), A(ascender), and D(descender) are often used to represent the symbols for building the encoded string from the digit string we discussed in the above section.

Now, how to convert the digit string into an encoded string? The process is rather lengthy, which is why most mailers use a USPS Intelligent Mail Barcode generator or outsource the job to a print and mail solution provider like PostGrid.

The size of an IMB should be within 22-24 bars per inch. The height and width of all IMBs must be in accordance with the USPS IMB specifications.

• The bar width must be within 0.015” to 0.0025” (0.038 cm – 0.063 cm)
• The space between two bars must be at least 0.012” (0.030 cm) and must never exceed 0.040” (0.101 cm)
• The length of all full bars must be within the range of 0.125” to 0.165” (0.317 cm – 0.419 cm)
• Trackers must be at least 0.039” high (0.100 cm) but should not exceed 0.057” (0.144 cm)

An Intelligent Mail Barcode generator can help you take care of these specifications.

IMBs can only be printed in designated areas of letters, flats, and postcards falling under the USPS size dimensions. It means that IMBs cannot be used for all types and sizes of mail. For being eligible to use IMBs on your letters, they should be at least 3.5” high and 5” wide. Letters cannot exceed 6.125” in length and 11.5” in breadth. The minimum dimensions are the same in the case of postcards, but postcards cannot cross 4.25” x 6”.

On letters, IMBs should be printed either on the barcode clear zone towards the lower right part of the envelope or the address block. For flats, the IMBs are supposed to be located on the address side of the mail item and at a minimum of 8.46 m away from the edges. Usually, they are printed just above the recipient's name and address.

How to Generate an IMB With PostGrid

PostGrid is USPS-compliant and fully supports IMBs. You can automatically send IMB-embedded mailpieces to your targeted mailing lists online. Our Direct Mail platform ensures the printing partners add an IMB to each mailer during production before shipping with the USPS. It also completes other tasks, like presorting and assembling. You don’t need to do anything extra or use different software. PostGrid follows all USPS barcode size, format, and placement rules to process your postal mail without hassles and ensure accurate IMB tracking.

Businesses can log into their PostGrid account, create a mail design using our professionally built templates, add their recipient address, and choose a delivery option. PostGrid can handle the rest, including printing, inserting the mail into envelopes, applying the IMB, and sending it through USPS. Adding the IMBs helps you track the sent mailers at every stage as they pass through the postal stream. 

Here’s a case study of how a Vegas-based insurance company wanted to send thousands of policy letters to customers monthly. It used PostGrid to print and ship all documents. PostGrid helped add IMBs to each envelope, making it easy for the firm to stay updated and follow up with the recipients on time. It also reduced customer complaints and mailing errors. The team saved hours of manual work and improved mailing speed and accuracy across all locations.

Direct mail sent and managed through the IMB system goes through pretty complex processes and involves a lot of checkpoints. The mainstream can be broadly divided into four parts as below:

1. Printing and Mailing

Anyone can print and mail their items with Intelligent Mail Barcodes, but it is advisable to take the help of a commercial printing and mailing vendor for setting up IMB tracing or a direct mail automation API like PostGrid. The IMB coding is complicated, and it is better to work with someone who has the experience and the necessary equipment to print IMBs perfectly as per the USPS guidelines.

As discussed earlier, only mail items with the specified size, weight, and format can use IMBs. Mailers should also take into account the barcode and address locations before printing.

2. Deposit at the USPS Entry Facility

The first IMB scanning will take place at the USPS entry facility after a few hours of deposit. All IMB mail items must be sent to an “Entry Facility,” also known as the “Network Distribution Center” (NDC). NDCs are regional warehouses, and there are a total of 21 NDCs in the US. All outgoing mail is sent to an NDC for sorting and routing.

Every NDC has huge high-speed sorting equipment to route every mailpiece to the next checkpoint using Intelligent Mail Barcodes. The next checkpoint could be another NDC or a destination facility. Every mail piece is scanned several times during the NDC processing procedure.

3. Routing to the USPS Destination Facility

After the NDC, your mail items are sent to a USPS “Destination Facility” or “Sectional Center Facility.” These facilities route mailpieces between the NDCs and the post offices nearest to the destination. The mailpieces are scanned again at SCFs and are routed toward the local post offices. There are about 195 SCFs across the US, and each one of them covers one or more 3-digit ZIP code prefixes.

4. Sending Mail to Local Post Offices for Delivery

Once the post offices receive the IMB mail items, there are more scan events before the final delivery. The post office is where the final scan event is done. Sometimes, scan events are completed right when the mail is out for delivery through geofencing.

Do IMBs and QR Codes Work the Same Way for Logistics?

An IMB and a QR code both help track items, but they are used in different ways. IMB is made for mailing through USPS. It has lines and bars that carry delivery and tracking details. USPS scans it at every step to track the mail. 

QR codes look like squares and are scanned with phones or devices. They can link to websites or store more types of data. IMB is best for sending mail in logistics, while QR codes are better for packages, inventory, or adding extra info that people or systems can scan and read easily.

We have successfully established that Intelligent Mail Barcodes have several advantages and should be used by every mailer. But, it is important to note that encoding IMBs isn’t easy, and the coding behind them is complex. PostGrid can help you create and print IMBs accurately and also track your mail items in real-time effortlessly.

PostGrid can also enable mailers to access and use CASS-certified addresses that have been already processed by the NCOA service. Not only that, PostGrid’s print and mail API can assist you in everything related to your direct mail marketing activities. So, whether it is making good use of IMBs or overall conducting powerful direct mail campaigns, PostGrid has got you covered.