Not found probably means that the standard "endpoint" (URL) for EWS (which is
https://servername/EWS/Exchange.asmx) is not there.
Which means that the server does not support EWS, or maybe it runs on a different server name.
Please ask your IT people / your mail provider's support specifically about EWS (aka Exchange Web Services) and what settings to use.
PS - built-in Email and the new Gmail use a different way to talk to Exchange, called ActiveSync.
EWS is also used by Mail Droid, EmClient, and others, so it's a valid choice too, as long as the server does not have it turned off (some do).
Also feel free to request a refund, I'm at kmansoft / gmail