| District | Post Town | Coverage | Postcodes |
|---|---|---|---|
| CO1 | Colchester | Colchester | 599 |
| CO2 | Colchester | Colchester | 940 |
| CO3 | Colchester | Colchester | 864 |
| CO4 | Colchester | Colchester | 1,187 |
| CO5 | Colchester | Colchester | 965 |
| CO6 | Colchester | Colchester | 1,012 |
| CO7 | Colchester | Wivenhoe, Great Bentley | 1,314 |
| CO8 | Bures | Bures | 124 |
| CO9 | Halstead | Halstead | 923 |
| CO10 | Sudbury | Sudbury | 1,656 |
| CO11 | Manningtree | Manningtree | 569 |
| CO12 | Harwich | Harwich | 635 |
| CO13 | Frinton-on-Sea | Frinton-on-Sea | 436 |
| CO14 | Walton-on-the-Naze | Walton On The Naze | 246 |
| CO15 | Clacton-on-Sea | Clacton-on-Sea | 1,360 |
| CO16 | Clacton-on-Sea | Clacton-on-Sea | 803 |