[4] RFC 2244 - ACAP -- Application Configuration Access Protocol, , https://tools.ietf.org/html/rfc2244#page-16
[3] RFC 3028 - Sieve: A Mail Filtering Language, , https://tools.ietf.org/html/rfc3028#section-2.7.3
CalDAV servers are REQUIRED to support the "i;ascii-casemap" and
"i;octet" collations, as described in [RFC4790], and MAY support
other collations.
[2] RFC 5260 - Sieve Email Filtering: Date and Index Extensions () https://tools.ietf.org/html/rfc5260