| Abbreviation | Definition |
|---|---|
| ID | Indonesia |
| IE | Ireland |
| IEO | International Exchange Office |
| IL | Israel |
| IMDAS | Intelligent Mail® Data Acquisition System |
| IMM | International Mail Manual |
| IMPAC | International Merchant Purchase Authorization Card |
| IMPC | Incoming Mail Processing Center |
| IN | India |
| INTELPOST | INTernational ELectronic POST |
| IO | British Indian Ocean Territory |
| IPA | International Priority Airmail |
| IPC | International Postal Coupon |
| IPCS | International Package Consignment Service |
| IPP | Irregular Parcels and Pieces |
| IPS | International Postal System |
| IQ | Iraq |
| IR | Iran |
| IRC | International Reply Coupon |
| IRT | Integrated Retail Terminal |