Strict require MTA option

Sieve language extension MTA options:  (0 or 1)
The  MTA option controls whether or not the MTA enforces "strict" syntax rules on the location of any    clauses  in Sieve filter scripts. The default is 0 (false), meaning that  clauses may appear anywhere in the Sieve script, not only at the very top of the Sieve script.

See also:
 * Sieve supported extensions
 * Sieve language extension MTA options
 * Sieve filter MTA options
 * Sieve language