In my example-
Server Name- ExchSRV1
Default web site- Default Web Site
New ECP Site- InternalECP
Domain Name- contoso.com
New ECP URL- ecp.contoso.com
1) Go into IIS, right click on Sites, Add Website.Name- "InternalECP"
Physical Path- "C:\inetpub\wwwroot2"
Binding, Type- https
IP address- All Unassigned,
Port- 443 (Feel free to use another port for added security.)
Host Name- "ecp.contoso.com"
2) On your DNS servers, make a DNS A record for "ecp.contoso.com" pointing to your exchange server IP address.
3) Open the Exchange Management Console and enter the following commands-New-EcpVirtualDirectory -Server "ExchSRV1" -WebSiteName "InternalECP" -InternalUrl "https://ecp.contoso.com/owa"
New-OWAVirtualDirectory -Server "ExchSRV1" -WebSiteName "InternalECP" -InternalUrl "https://ecp.contoso.com/owa"
4) Test that you can log into the new url and get into ECP.
5) Enter the following to disable ECP on the main site-
Set-EcpVirtualDirectory -identity "ecp (Default Web Site)" -AdminEnabled $false