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Gracefully Handling Microsoft AutoDiscover Inquiries

Rachel Moorehead

New Pleskian
Greetings!

Environment:
RHEL 6.6
Plesk 12.0.18 RedHat el6 1200151014.14

Background: We've recently switched to a Microsoft Exchange based email service. As a part of the email client configurations, Microsoft uses a utility called AutoDiscover. AutoDiscover has a predefined set of URLs that it attempts to connect to in order to find its Exchange server. Unfortunately the first URL it tries is https://emaildomain.com/autodiscover/autodiscover.xml. Which for most people "emaildomain.com" is also their primary website domain so this traffic gets served to the web server first, which provides a 500 response and AutoDiscover moves on to its next predefined URL to try.

For a hosting provider with hundreds of web domains that are also email domains, this is slowly becoming a load and log growth problem as AutoDiscover attempts to connect every time an email client is open and hits the server at least 5 times in one pass.

Question: Is there a quick, easy way to say for any https://*/autodiscover/autodiscover.xml that gets served to Plesk to deny with little server-side overhead?

Here is a log snippet for example:

<ip address> - - [30/Dec/2015:10:54:07 -0500] "POST /autodiscover/autodiscover.xml HTTP/1.1" 500 17666 "-" "Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 16.0.4266; Pro)"
<ip address> - - [30/Dec/2015:10:54:45 -0500] "POST /autodiscover/autodiscover.xml HTTP/1.1" 500 16000 "-" "Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 16.0.4266; Pro)"
<ip address> - - [30/Dec/2015:10:59:26 -0500] "POST /autodiscover/autodiscover.xml HTTP/1.1" 500 16000 "-" "Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 16.0.4266; Pro)"
<ip address> - - [30/Dec/2015:11:01:06 -0500] "POST /autodiscover/autodiscover.xml HTTP/1.1" 500 17666 "-" "Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 16.0.4266; Pro)"
<ip address>- - [30/Dec/2015:11:04:36 -0500] "POST /autodiscover/autodiscover.xml HTTP/1.1" 500 17666 "-" "Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 16.0.4266; Pro)"
 
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