<rule name="Reverse Proxy to some other domain" stopProcessing="false">
<match url="^(.*)" />
<action type="Rewrite" url=http://someotherdomain.com/{R:1} />
<serverVariables>
<set name="HTTP_SOME_CUSTOM_HEADER" value="FOO_BAR" replace="true" />
</serverVariables>
</rule>
This no longer works; I'm getting a 500 error. I had to comment out my <set> tags to get this to work.
I already had an issue with this (here) in a separate post that I had to work around using a managed IHttpModule. Any ideas?