IIS with an exchange back-end isn't responding to valid queries, but will throw 400 Bad Request for invalid queries.

From localhost PS:

> telnet 80
GET / HTTP/1.1

HTTP/1.1 400 Bad Request
[ etc. ]

> telnet 80
GET / HTTP/1.1

[no reply]

This is the same error from other hosts, and IIS is listening on 443, 80, and 444.

  • Did you try the actual IP address? Not the loopback address. – hot2use Jul 19 '17 at 20:43
  • @hot2use Yes, telnetting has the same issue. – Kenneth B. Jensen Jul 19 '17 at 20:44

Exchange back end site in IIS uses 81 for http and 444 for https. The default website use 80 and 443.

If you install CAS role and Mailbox role on seperated servers, telnet 80 and 443 on CAS server while telnet 81 and 444 on mailbox server.

If users are able to access OWA and ECP, it means there is no problem about network connection or binding issues. If OWA or ECP doesn't work, analysis IIS logs and application logs for clues.

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