IDXblue gives you the option to require your leads to enter their phone number.

When a buyer is searching MLS listings using IDXblue on your web site, at times they are asked for their personal contact information. We call that process fencing. Until recently, the buyers were required to complete only the name and email address fields of the contact form. If a required field is left blank, the user cannot continue.

IDXblue now lets you require your leads to enter a phone number. 

To update your IDXblue settings and make the phone number required, visit the setup area, then click Install & Manage, then Other Settings, and check the box labeled Require Phone Number.

Two important notes:

1. Remember IDXblue still gives you the freedom NOT to require the phone number — that is, to leave the phone number voluntary.
2. By default, the phone number is a voluntary field. If you want to keep it that way, nothing is required on your part.