cPanel allows you to use several web interfaces at once for viewing mail, sometimes they can be disabled or perhaps some of them need to be disabled.
Settings are in “WHM” – “Server Configuration” – “Tweak Settings” – tab “Mail“
Where can I specify On or Off opposite Enable Horde Webmail, Enable RoundCube Webmail or Enable SquirrelMail Webmail.
To save changes, click the button below “Save“.
You can connect to the web interface on port 2096, for example, https://ixnfo.com:2096