Spooling and custom transports

• Configurable and replaceable spooling mechanism
  • Instant spool (no spooling - instant send)
  • Memory spool (queueing and kernel.terminate event flush)
• Some custom transport for a kind of fail-proof installations
  • Chained transport (meta-transport which uses other transports with priority list)
  • Retry-on-failure transport (meta-transport which uses single tranport several times until timeout\retry-count or success)