We love the SBX for small business customers. It just works - until you are asked to use SIP trunks. Has anyone found a SIP provider that works reliably on SBX? I know the "certified" providers are suppose to be reliable but there seems to be different definitions of "reliable". My definition of reliable is that the SIP trunks work as long as the Internet provider is up and running. Some techs think having to reset the SBX on a monthly basis because the SIP trunks lock up is acceptable. Not to my customer its not! What have you found? Thx

You said it yourself, they are only as reliable as your internet provider's bandwidth. I found them to be slightly less reliable than voip trunks, some might disagree.

Update:
One of two SIP trunk customers we have on SBX is a 24/7 operation. They would have to re-power the SBX monthly to get the SIP working again. Usually in the early hours of the day. Finally we replaced the SIP with PRI. It is disgusting that it had to come to this. We handle a much larger VOIP system that has 0 problems with the same carriers SIP trunks. FYI

I know the MBX had a problem that when it lost registration it would stop trying to re-register. Never did sip on an sbx so not sure if they share the same plight (mbx did get fixed, after months of endless logs etc and lost customers). Intermedia is A+ for provider.