There are 11 words that start with 'postb'.
| postbag | postbox | 
| postboy | postbags | 
| postbase | postboys | 
| postburn | postboxes | 
| postbellum | postbiblical | 
| postbourgeois | |
Note: These 11 words that start with 'postb' are found from the USA & Canada version of the tournament Scrabble word list.