[1] [[FTPメールの日時形式]]


[2] [CITE@en[RFC 524 - Proposed Mail Protocol]], [TIME[2021-01-31T11:00:07.000Z]], [TIME[2021-03-10T05:27:36.878Z]] <https://tools.ietf.org/html/rfc524>

[3] [CITE@en[RFC 539 - Thoughts on the mail protocol proposed in RFC 524]], [TIME[2021-01-31T11:13:10.000Z]], [TIME[2021-03-10T05:30:45.819Z]] <https://tools.ietf.org/html/rfc539>

[4] [CITE@en[RFC 555 - Responses to critiques of the proposed mail protocol]], [TIME[2021-02-01T01:59:11.000Z]], [TIME[2021-03-10T05:31:39.630Z]] <https://tools.ietf.org/html/rfc555>

[5] [[RFC 561]]