Sieve hierarchy

Messaging Server&#x27;s Sieve implementation has, as its most significant, major extension to Sieve, a nonstandard one: the ability for multiple scripts to apply to a single recipient. (The Sieve specifications assume a single Sieve script per user.) The MTA supports a number  of types of Sieve scripts, whose specified effects are combined to result in an overall Sieve effect for each user.

Sieve scripts come in two general classes, system-level vs. user-level. Within these classes there are multiple different types of Sieve scripts. Such multiple Sieve scripts are combined in a logical order, as discussed in Sieve filters: semantics of multiple scripts. Then such multiple Sieve scripts are evaluated in a logical order, as discussed in Sieve filters: evaluation of multiple scripts.

See also:
 * Sieve filters: types of scripts
 * Sieve filters: semantics of multiple scripts
 * Sieve filters: evaluation of multiple scripts
 * Sieve filters