| Abbreviation | Definition |
|---|---|
| MQC | Mailpiece Quality Control |
| MR | Mauritania |
| MRB | Management Review Board |
| MRC | Mail Recovery Center |
| MS | Montserrat |
| MSC | Mail Service Center |
| MSC | Management Sectional Center |
| MSSP | Manpower Scheduling and Staffing Program |
| MT | Malta |
| MTAC | Mailers Technical Advisory Committee |
| MTE | Mail Transport Equipment |
| MTESC | Mail Transport Equipment Service Center |
| MTN | Mountain |
| MTTR | Mean Time To Repair |
| MU | Mauritius |
| MV | Maldives |
| MVO | Motor Vehicle Operator |
| MVRF | Mobile Vehicle Repair Facility |
| MW | Malawi |
| MX | Mexico |