Balance 380 - Inbound Firewall Rules

How can I restrict inbound traffic by a FQDN instead of an IP address? We have a SIP trunk and I need to open up ports but only for my SIP provider.

For the inbound traffic the domain name resolve is done on client side. Therefore, server will not know what’s original FQDN of the inbound traffic.

For the SIP trunk provider, they should give you their IP addresses.