both IMAP system flags and IMAP keywords.
whether a flag belongs to a list.
capabilities.  First, it allows manipulation of sets of IMAP flags.
enables support for multiple variables containing sets of IMAP flags.
MUST cause an error according to [SIEVE].
actions, the "hasflag" test and the ":flags" tagged argument.
requirement is to simplify amalgamation of multiple flag lists.
If a flag validity check fails, the flag MUST be ignored.
string containing a space-separated list of flag names.
flags in lists or the preservation of their case.
setflag/addflag/removeflag actions and the hasflag test is optional.
execution.  If the SIEVE interpreter doesn't support the "variables"
will cause a runtime error [SIEVE].
The "addflag" action adds flags to an existing set.  The "removeflag"
internal variable also applies to the implicit keep.
2.10.3 of [SIEVE]), the last flag list value MUST win.
Setflag is used for setting [IMAP] system flags or keywords.
Setflag replaces any previously set flags.
Removeflag is used to remove flags from a list of [IMAP] flags.
variables is omitted, value of the internal variable is used instead.
insensitive comparison as defined for IMAP flags by [IMAP].
counts of the member variables.
hasflag :contains "MyVar" "junk forward"
hasflag :contains "MyVar" "forward junk"
However, the last two forms are not recommended.
hasflag :count "ge" :comparator "i;ascii-numeric"
evaluates to true, as the variable contains 2 distinct flags.
alters the behavior of actions "keep" and "fileinto".
listed after the :flags tagged argument.
to store any flag as a runtime failure to execute the Sieve script.
IMAP client or may have direct access to the mailstore.
keep (see Section 2.10.2 of [SIEVE]).
if header :is "From" "boss@company.example.com"
# "Big \Answered $MDNSent" when filed into mailbox "grandma".
if header :is "Sender" "owner-ietf-mta-filters@example.org"
elsif anyof address :domain :is ["From", "To"] "company.example.com"
# Move all other external mail to "personal"
Guenther, Rob Austein, Sam Hartman, Eric Gray, and Cullen Jennings.