I'm fairly sure the D95 no longer can use gmail directly as I am pretty sure it does not support SHA-2.
This would show itself by giving a protocol error, and typically a fault code (017-714 if I remember correctly)
If that is the case you would need to call Xerox to process a FER (Feature Enhancement Request) to get the SHA-2 Encryption added in a firmware update (this is not a guarantee it would be done)
It is also possible they already have a firmware update that works, but there is no note of SHA-2 being added in the current general release available on Xerox.com.
General release = 1.204.9
Spar (Latest) - 1.201.1
I am not sure of the reasoning behind the number being lower on the latest spar release, just call up Xerox and ask for a link to it if needed, I could find nothing on any of my sources to get a download link, Sorry.
Best bet is to just call Xerox if you have a maintenance agreement. The production machines are harder to source the firmware for.
In the meantime, SMTP2GO should work.