The MAL API is enhanced by additional constants for the c.o.mail.MailListField enum class and c.o.mail.MailSortField enum class respectively:

- Flag \Answered
Column=657, Name=answered

- Flag \Forwarded
Column=658, Name=forwarded

- Flag \Draft
Column=659, Name=draft

- Flag \Flagged
Column=660, Name=flagged

Thus it is possible to retrieve mail messages sorted by other flags than only by \Seen

Note: Sorting by Flag \Forwarded requires the mail service to support either a \Forwarded system flag or user flags. In case of IMAP the user flags capability needs to be supported in order to sort by that field.