MWI not lighting with Exchange 2010 UM

[moorelock]

SO, we've got everything working except for the MWI lighting on the phones.  We see a SIP NOTIFY coming from the UM, but get a 503 - Service Unavailable error on the UM from the Mitel system.  I believe the SIP Trunk and SIP profile are configured correctly as we are able to leave a voicemail and get email notification.  We have the extensions listed in the SIP Peer Profile Assignment form as suggested in another post in the forum.  Any ideas as to why we are getting the 503 error from the Mitel?

[martyn]

Not entirely sure if it's related as I haven't done an integration like this yet, but check out KB 11-5191-00242 that just got published on MOL, as it relates to Exchange 2010 SP1 and MWI's.

[brantn]

I would verify the setup guide on MOL paying close attention to COS options. You also need to make an incoming DID SIP Peer profile assignment for your subscriber access number. Restart the services and try again.

I have run across this multiple times. Try those and repost I will post my options if needed after that.