No special actions are required after upgrading. However, one point
is worth noticing. Until now, it was an error to specify two
prog definitions with the same handler name. This rule
however, applied only to generic milter handlers, special handlers
(begin, end, startup, shutdown) being exempt
from it. Starting with version 8.17, multiple prog
declarations with the same handler name are allowed for all handlers.
See Multiple handler definitions, for details.