In some cases, autodiscover requests can create numerous 404 errors. If the Exchange server is configured to reach out to a domain used by a website and the file autodiscover.xml file does not exist there, IIS logs will show thousands of 404s every day. In the case of Office 365, autodiscover requests will always be routed to the domain.
For example, https://domain.com/autodiscover/autodiscover.xml.
These additional requests are unlikely to create significant site traffic, though it still may be helpful to remove prevent the 404s from logging by fixing the issue.
Please see this forum post where a solution is listed.
"The solution to stop the 404s ... is to have a simple redirect in IIS so it processes a redirect.
(Make a seperate directory called autodiscover and redirect all traffic to https://autodiscover.ourdomain.com/autodiscover/autodiscover.xml)
The server will still process this and the same small overhead but there will be no 404s."
If Office 365 is not used, it may also be possible to reconfigure the URL to the autodiscover.xml file.