Please help!
I am trying to receive an unsolicited NOTIFY in my application, but the SIP Stack keeps rejecting it with 400 Bad Request.
Does anybody know if unsolicited NOTIFY is supported? If it is not, I would expect receiving 481 Subscription does not exist.
What else could cause the 400 response?

The NOTIFY sent to the device is

NOTIFY sip:78006@MyIP SIP/2.0
Via: SIP/2.0/UDP;branch=z9hG4bK-ku4we9-3-yip;rport
Max-Forwards: 70
To: <sip:78006@MyIP>
From: <sip:78005@MyDomain>;tag=ku4we9-v74
Call-ID: ku4we9-hcb-2@
Content-Type: application/simple-message-summary
Content-Length: 98
Event: message-summary

Messages-Waiting: yes

Thanks in advance!