sieve_extensions: fileinto reject vacation imapflags notify envelope
relational regex subaddress copy

Space-separated list of Sieve extensions allowed to be used in sieve scripts, enforced at
submission by timsieved(8). Any previously installed script will be unaffected by this option
and will continue to execute regardless of the extensions used. This option has no effect on
options that are disabled at compile time (e.g., "regex").

Allowed values: fileinto, reject, vacation, imapflags, notify, include, envelope, body,
relational, regex, subaddress, copy