Zimbra Supports HTTPs by Default:
By default Zimbra will use HTTPs support only and disable HTTP use on the webmail client. But users will always use non http port to access the webclient. Users do not like to type https before the domain each time to get into the webmail client. Zimbra uses Nginx to run the proxy services to access the Javamail Client of Zimbra. Zimbra supports 5 types of proxy services through Nginx:
You may check the following for details:
How to Redirect HTTP to HTTPs automatically in Zimbra 8.8*
The most popular out of 5 options for proxy services, is to redirect. To do this, you can run the following:
zmprov ms `zmhostname` zimbraReverseProxyMailMode redirect
This will redirect your URLs to the zimbra hostname based HTTPs.
Now, restart the proxy services:
su - zimbra zmproxyctl restart
Hope this helps.