This member is added by an implicit conversion from OverlaySetting[T] to
any2stringadd[OverlaySetting[T]] performed by method any2stringadd in scala.Predef.
This member is added by an implicit conversion from OverlaySetting[T] to
StringFormat[OverlaySetting[T]] performed by method StringFormat in scala.Predef.
(Since version 2.3) durable mailboxes are superseded by akka-persistence