I think you should ask them what section to change. Presumably if they know that there is a section with their IP address in it, then they can tell you where it is. For example, and this is only a very broad example, say they had something like this in your web.config file:
Code:
<AppliedI_Section>
<AppliedI_IP_Address="123.456.789.000"/>
</AppliedI_Section>
Surely they should be able to identify something like that for you. We don't have any IP address data in our web.config file, or other smtp/email entries either.