Contains the private notes that can be attached to messages. "Private" in this context means that the notes are not exported to the outside by way of the mail transport system.
> Columns
mail_id: integer, unique
Unique internal identifier of the message. This is a foreign key
to mail.mail_id.
note: text
Text of the note. It should never be empty, because the application
code should delete the row when the text is cleared.
last_changed: timestamp
The date and time when the note was last modified.
> Size
One row per message to which a note is attached.