Learn how many policies you can create on IMSS.
There is no limitation for number the rules or policies that can be defined. However, the maximum total size of one rule setting is 640K. The total size includes rule route (sender/recipient), rule filter (scanning condition), and rule action.
IMSS can support at least 10,000 sender/recipient settings for a rule route, supposing that each email address/LDAP account has 20 characters.