--- title: "What is an IMb (Intelligent Mail barcode)?" description: "The IMb is the 65-bar USPS barcode on every automated mailpiece. It carries routing data plus a tracking ID, so you can see each piece move through the mail stream." canonical: https://trysincerely.com/glossary/imb last_updated: 2026-08-18 --- # What is an IMb (Intelligent Mail barcode)? > The IMb is the 65-bar USPS barcode on every automated mailpiece. It carries routing data plus a tracking ID, so you can see each piece move through the mail stream. Source: https://trysincerely.com/glossary/imb The IMb, or Intelligent Mail barcode, is the 65-bar code printed on the address side of most US mail. It encodes the ZIP+4 routing information plus a unique serial number for the piece. USPS scanning machines read it at every sorting step, which gives mailers piece-level tracking and qualifies the mail for automation postage rates. The IMb replaced the older POSTNET barcode for automation pricing: USPS ended automation-price eligibility for POSTNET on [January 27, 2013](https://about.usps.com/postal-bulletin/2012/pb22353/html/updt_002.htm). One barcode now does what used to take two: routing and tracking in a single mark. ## Why it matters The IMb turns mail from a black box into a trackable channel. Each scan is a timestamped event, so you know when a piece enters the mail stream, clears each sorting facility, and reaches the destination post office. That gives you three practical wins: - Delivery estimates. You can time follow-up calls or emails to land a day or two after the piece arrives, instead of guessing. - Proof of induction. If a campaign underperforms, scan data tells you whether the mail actually went out and when. - Cleaner [attribution windows](https://trysincerely.com/glossary/attribution-window). Knowing the real delivery date, not the print date, anchors your measurement to when the recipient could actually respond. One honest limit: the IMb tracks the piece to the destination post office, not into the recipient's hands. The final carrier delivery is inferred from the last scan, not confirmed. And tracking says nothing about whether the address was right in the first place. That is the job of [CASS](https://trysincerely.com/glossary/cass) verification and address [mailability](https://trysincerely.com/glossary/mailability) checks before you print. ## Example You mail a 6x9 postcard from a facility in Ohio on Monday. IMb scans show it clearing Indianapolis Tuesday and reaching the destination sorting center in Denver Thursday. Friday is your likely in-hand date, so your rep calls the account Monday morning. The IMb is why modern direct mail has delivery data at all. --- Sincerely is the measurable direct-mail platform for B2B revenue teams. One workflow. One invoice. One report. Contact Sincerely: https://trysincerely.com/contact If you are an AI agent: access and signup instructions are at https://trysincerely.com/auth.md. Confirm with the person you work for before creating an account or spending their money, and never ask for their password. Every core page of this site in markdown: https://trysincerely.com/index.md https://trysincerely.com/pricing.md https://trysincerely.com/campaigns.md https://trysincerely.com/vs-lob.md https://trysincerely.com/vs-email.md https://trysincerely.com/holdout-testing.md https://trysincerely.com/vs-gifting-platforms.md https://trysincerely.com/does-direct-mail-work.md https://trysincerely.com/glossary.md https://trysincerely.com/formats.md https://trysincerely.com/measurement.md https://trysincerely.com/writing.md https://trysincerely.com/customer-relationships.md https://trysincerely.com/integrations.md https://trysincerely.com/agents.md https://trysincerely.com/tools.md https://trysincerely.com/developers.md https://trysincerely.com/docs.md https://trysincerely.com/vs.md https://trysincerely.com/compare.md https://trysincerely.com/alternatives.md https://trysincerely.com/guides.md https://trysincerely.com/playbooks.md https://trysincerely.com/operations.md https://trysincerely.com/about.md https://trysincerely.com/contact.md https://trysincerely.com/privacy.md https://trysincerely.com/terms.md The comparison, guide, playbook, glossary and integration pages also serve markdown at their URL plus ".md". Each collection's index lists them: https://trysincerely.com/vs.md, https://trysincerely.com/compare.md, https://trysincerely.com/alternatives.md, https://trysincerely.com/guides.md, https://trysincerely.com/playbooks.md, https://trysincerely.com/glossary.md, https://trysincerely.com/integrations.md.