Here are the steps to setup your number as eFax to receive incoming fax directly on one or more emails.
Login to your dashboard and go to section Manage Phone System > Users(Extensions).
Click Add New and fill in details as per shown in image. You can add multiple emails separated by comma (,) if you wish to receive incoming fax on multiple emails or allow multiple emails to use this number for sending outgoing fax via email. Click Save to create extension.
Now go to section Manage Phone System > Manage Phone Numbers. Select the number you want to use as eFax and click Edit Selected. This will open a menu on right hand side section. Select Destination Type as E-Fax & Destination as the eFax extension you created. In my case it is extension 250. Click Update to save the changes.
You configuration for the number should look like this after this step.