RFC 6154, "IMAP LIST Extension for Special-Use Mailboxes", March 2011Source of RFC: morg (app)
Errata ID: 4422
Status: Held for Document Update
Reported By: Chris Newman
Date Reported: 2015-07-20
Held for Document Update by: Barry Leiba
Date Held: 2015-07-20
Throughout the document, when it says:
It should say:
There is missing information in this RFC that resulted in interoperability problems when we performed an informal interop test of multiple implementations on 2015-07-19. This is assumed to be a "hold for document update" errata.
There is no guidance in the document related to how special-use attributes are bootstrapped. Servers may pre-create them but there's no requirement to do so and clients may use the CREATE-SPECIAL-USE or METADATA extensions to bootstrap but there is no requirement to use those mechanisms if the server offers them. This resulted in a server implementation assuming the client would bootstrap these attributes and a client assuming the server would do so, thus interoperability failed.
Given this experience, the fastest way to resolve this interop problem over time is for both client and server to take responsibility for bootstrapping special use mailboxes. This means if clients create a mailbox intended for special use (e.g., drafts, sent, junk, trash, etc), and the CREATE-SPECIAL-USE extension is offered, then clients need to provide the USE extension to improve interoperability. Servers that are provisioned with an end-user's locale or language need to pre-create appropriate special-use mailboxes to improve interoperability of this extension. For existing accounts where the server is upgraded to support this feature, the server can look for mailboxes with names that imply special use and add the attribute to those mailboxes (especially if the server has locale/language awareness provisioned for users). Clients that implement a name-based search if special use attributes are not present and decide to use a mailbox for a special use based on its name can use the METADATA extension, if offered, to label that mailbox appropriately.