I think I better understand your issue now.
My previous post mainly pertains to incoming SNMP managment traffic, which is allowed on any VRF. However outbound management traffic is only sent out via the Default VRF or the configured Mangement VRF as Sargis detailed.
Your SNMP management device will need to either be on the default VRF or on the configured Management VRF.
Michael Morey
Principal Technical Support Engineer
Extreme Networks