Please note: This article is for users with very good CRM skills only.
However, before you follow the below instructions, please contact us via support@mscrm-addons.com.

1) In order to bypass the IFD authentication, you need to edit the ptm_WebApplicationPreloaderGeneralScript webresource in Dynamics 365.

2) Look for  

appUrl = SetQueryString(appUrl, "isOutlook", $ptm.isOutlook + '');

and replace it with

appUrl = SetQueryString(appUrl, "isOutlook", $ptm.isOutlook + '');

var userIDCrm = $ptm.context.getUserId();

if ((userIDCrm == null) || (typeof (userIDCrm) == "undefined")) {

userIDCrm = parent.Xrm.Page.context.getUserId();

}

appUrl = SetQueryString(appUrl, "ORIFDI", userIDCrm + '');

3) Next, save your changes and publish them.

4) Open your IIS. In there, turn on Anonymous only and add a CRM system administrator to this authentication mode.

5) Restore the original WebConfig and WebApplication Port and change the Connection Profile for the tool to OnPremise.

That’s it! We appreciate your feedback! Please share your thoughts by sending an email to support@mscrm-addons.com!