Name: mailbox_initial_flags
Type: STRING
Default-Value: NULL
Last-Modified: 2.5.0

space-separated list of permanent flags which will be pre-set in every
newly created mailbox.  If you know you will require particular flag names
then this avoids a possible race condition against a client that fills the
entire 128 available slots.  Default is NULL, which is no flags.

Example: $Label1 $Label2 $Label3 NotSpam Spam
