5. メモキーワード

5.1. $hasmemo

5.2. $memo

The $memo and $hasmemo keywords support user-created notes or annotations attached to messages. $memo is applied to the memo message itself, while $hasmemo is applied to the original message being annotated. They are mutually exclusive.

When a client creates a memo, it MUST add $hasmemo to the annotated message and $memo to the memo message. When a memo is deleted, it MUST remove $hasmemo from the annotated message. Messages with $memo SHOULD be stored in a mailbox with the Memos mailbox name attribute when available, and supporting clients MUST present them as contextual annotations rather than ordinary standalone messages.