cairn/changes/imap-sasl-ir-override/delta.md
IMAP SHALL accept an imap.sasl-ir override deciding whether the RFC 4959 initial response is sent inline with AUTHENTICATE. false never inlines and waits for the server's continuation request, true always inlines, and unset follows the advertised SASL-IR capability. The override applies to every SASL mechanism, because a server that mishandles the inline form does so in its command parser rather than per mechanism.
Coremail (126.com, 163.com) SHALL be treated as advertising SASL-IR without honouring it: it answers the inline initial response with a tagged BAD. Such an account needs imap.sasl-ir = false, and (per the ID quirk) usually imap.id.auto = true as well.