[4] [CITE@en[RFC 2244 - ACAP -- Application Configuration Access Protocol]], [TIME[2021-04-11T10:25:16.000Z]], [TIME[2021-04-21T09:50:14.643Z]] <https://tools.ietf.org/html/rfc2244#page-16>

[3] [CITE@en[RFC 3028 - Sieve: A Mail Filtering Language]], [TIME[2021-04-11T10:35:14.000Z]], [TIME[2021-04-21T09:35:01.781Z]] <https://tools.ietf.org/html/rfc3028#section-2.7.3>

[FIG(quote)[
[FIGCAPTION[
[1] [CITE@en[RFC 4791 - Calendaring Extensions to WebDAV (CalDAV)]]
([TIME[2016-01-10 08:25:07 +09:00]] 版)
<https://tools.ietf.org/html/rfc4791#section-7.5>
]FIGCAPTION]

> CalDAV servers are REQUIRED to support the "i;ascii-casemap" and
>    "i;octet" collations, as described in '''['''RFC4790''']''', and MAY support
>    other collations.

]FIG]


[2] [CITE@en[RFC 5260 - Sieve Email Filtering: Date and Index Extensions]]
([TIME[2017-05-07 22:48:17 +09:00]])
<https://tools.ietf.org/html/rfc5260>