Clients roundcube access or how user can read email

Hello,

I have a firewall that controls who can access web panel. All ports are closed.
https://wiki.centos-webpanel.com/centos-mostly-used-ports , except 2083
But when user / client opens Roundcube and it gets redirected to 2087, but for me it is closed.
So the main question is how a user can access his Roundcube or email?
I think there should be a fix and client should be redirected from 2083 to 2083 not 2087. But there is no such site.

Try to use links like http://domain.tld/webmail