RFC 6154, "IMAP LIST Extension for Special-Use Mailboxes", March 2011Source of RFC: morg (app)
Errata ID: 5431
Reported By: Bron Gondwana
Date Reported: 2018-07-19
Rejected by: Alexey Melnikov
Date Rejected: 2018-07-26
Section 2 says:
An IMAP server that supports this extension MAY include any or all of the following attributes in responses to the non-extended IMAP LIST command.
It should say:
An IMAP server that supports this extension SHOULD include any or all of the following attributes in responses to the non-extended IMAP LIST command.
There exist clients which send a non-extended LIST command and will correctly display and interact with mailboxes usefully if their special-uses are given in the response.
Because of this, many servers are already replying with the special-use attributes, and there are no known reports of clients being broken by that behaviour. Because of this, the MAY should be raised to a SHOULD, and server implementations should default to turning this on.
The right way to make this change is to revise the document. MAY was intended at the time of publication.