Greetings;
It was as I expected, the vps hosting company had closed port 993. I had them open it back up and all is well!
For the information of others, Gmail also blocked logins from my vps instance after port 993 was opened. In the roundcube error logs, there was text saying to login to the account from a web browser. I received this in an email from Gmail:
"Someone recently used your password to try to sign in to your Google Account xxxx@gmail.com. This person was using an application such as an email client or mobile device.
We prevented the sign-in attempt in case this was a hijacker trying to access your account..."
The email listed the IP address of my vps, and the time of the attempted login. It directed me to go to special google url and sign in. After I signed in I was asked if I wanted to allow the other "device" to sign in. I clicked yes, and now it works. I can access gmail from within Epesi.
Gmail added a few extra steps to get this going, but I appreciate the added security.
Thanks Epesi team, for creating and supporting such a wonderful application!