What webservers are needed for office 365 activation?

The network planning guidance at https://docs.microsoft.com/en-us/office365/enterprise/network-planning-and-performance is a great place to start for these type of issues. I highly recommend reading through all of this content and implementing the guidance by Microsoft. They have a lot of very good reasons to make changes to your network and your engineers need to get up to speed on what they need to do to provide a secure and highly performant experience to the users at a variety of locations and devices.