http://msexchangeguru.com/2013/01/16/eac-exchange-2013/


Exchange Administration Center (EAC) replaces the Exchange Management Console (EMC) and the Exchange Control Panel (ECP), which were the two interfaces that were used to manage Exchange Server 2010. It is the web-based management console in Microsoft Exchange Server 2013 that allows for ease of use and is optimized for on-premises, online, or hybrid Exchange deployments.

One of the advantages of having the web-based EAC is that you can partition access from the Internet/Intranet from within the ECP IIS virtual directory to allow or disallow management features. This allows you to permit or deny access to users trying to access the EAC from the Internet outside of your organizational environment, while still allowing access to an end-user’s Outlook Web App Options

Because the EAC is now a web-based management console, you will need to access it by using your web browser using the ECP virtual directory URL. To find the ECP virtual director URL that you need to access the EAC in most cases the EAC’s URL will look similar to the following:

Internal URL: https://<CASServerName>/ecp   the internal URL is the URL that user’s access the EAC from within your organization’s firewall.

External URL: https://mail.contoso.com/ecp   the external URL is the URL that user’s access the EAC from outside of your organization’s firewall.


To find the Internal or External URL for the EAC, use the Get-ECPVirtualDirectory cmdlet

Get-ECPVirtualDirectory | Format-List Name,InternalURL,ExternalURL

If you are trying to access EAC for the first time and your mailbox is on Exchange 2010, you need to use the URL in the format:

https://Exchange2013ServerName/ecp?ExchClientVer=15

This is because in a co-existence scenario, your mailbox is still housed on the Exchange 2010 mailbox server, the browser will default to the Exchange Server 2010 ECP. Now if you want to access the Exchange 2010 ECP and your mailbox resides on an Exchange 2013 mailbox server, use the following URL:

https://Exchange2010ServerName/ecp?ExchClientVer=14.


added by myself:

if you want to login(ex2013) outlook web app in a co-existence，you needed type 

https://exchange2013.contoso.com/owa