It is possible to block Web Mail using Web Control, which is great. However we are corporate users of Gmail. With most competing products it is possible to use the inclusion of a specific header to enable gmail to apply controls as to which domains can be logged into - see https://support.google.com/a/answer/1668854?hl=en. As is it is not possible to allow access to corporate gmail but disable access to personal gmail. This is a significant feature missing.