A message-flags notification is produced whenever a status flag has changed because the email message was:
When a message-flags notification is sent, the notification carries the following properties:
The flags set for the email message before its status changed
The flags set for the email message after its status changed
This information is carried in two properties, oldflags and newflags, which are 5–character strings.
For a description of the values of these two properties, see Syntax for newflags and oldflags Properties.