I have been an early adopter of VoiP,  After trying Vonage for a while I moved to AT&T’ callvantage service, which I really like because of the features it offers me over normal phone service  I installed two lines in my SF home and two lines in my Sonoma home  Everything was fine until E911 came alone.  AT&T decided to use E911 because of pressure from the FCC etc  That is fine but then it turns out that as part of their procedure, they verify the address they have been given  They do this using the post office system.  My home in
Sonoma is in a private community (we own the roads) and the post office will not serve us although Fed Ex, UPS etc have no problem.  We also definitely have 911 service if you have a normal phone.  Since they could not verify my address using their normal process, they have sent me a letter saying they will discontinue my service as of Jan. 2^nd.  I have spent hours on the phone with them about this since the first indication I got that there was a problem was our inability to dial out on one line,  They will not accept my statement that I live were I live  They will not make any effort to determine that this is indeed a good address  They basically told me was not worth their effort to keep me as a customer.    I have not tried Vonage to see if they have a different policy but I will look into it shortly.