I think this customer has a version 8 IP office in basic mode. Can I use Stunnel to integrate voicemail to email capability? Usually I am working on essential edition with stunnel. Also it may be a v9, what is the oldest version that can use gmail without stunnel? I recall R9 but not sure.

I'm not sure anything older than v10.0 will work with Gmail anymore. Something about TLS v1 possibly. It definitely won't work directly with Gmail if you don't have the STAR/TLS option.