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Internet-Draft This document extends the IMAP OBJECTID specification in RFC8474, which describes persistent identifiers for Mailboxes, Emails, and Threads in email. Some servers may be unable to provide persistent identifiers for some data types, but be able to provide them for others. This extension allows a server to specify that it can provide some objectids, without needing to implement all data types.

OBJECTID=MAILBOX If a server has the capability OBJECTID=MAILBOX then it supports the objectids for mailboxes described in section 4.

OBJECTID=EMAILID If a server has the capability OBJECTID=EMAILID then it supports the objectids for emails (and optionally threads) described in sections 5 and 6.

Supporting multiple datatypes An implementation which supports both MAILBOXID and EMAILDID SHOULD only issue the capability OBJECTID as defined in . Clients are recommended to check for both the specific or general capability when deciding what requests to send.

IANA considerations IANA is asked to register the capabilities OBJECTID=MAILBOX and OBJECTID=EMAILID with reference to this document.

Security considerations This document does not introduce any security considerations beyond those described in .

Acknowledgements Daniel Eggert, Ken Murchison, Matt Diephouse, the bar at Melia Castilla in Madrid.

This document updates RFC 3501 (IMAP4rev1) with persistent identifiers on mailboxes and messages to allow clients to more efficiently reuse cached data when resources have changed location on the server.

Changes from Earlier Versions [[This section to be removed by RFC Editor]]

draft-ietf-mailmaint-imap-objectid-partial-00 renamed for adoption removed the MUST around client behaviour; clients can choose not to use OBJECTID any time they want. There's no MUST here. tidied up wording a bit (I may not have been 100% sober when I wrote the initial draft)

draft-gondwana-imap-objectid-partial-00 Initial version