It is not possible to send faxes from PBX Solution, though it is possible to receive them and optionally forward them to an email address.
1. In order to receive faxes activate fax on an account from customer portal.
2. or activate UM on the account in porta and update UM Preferences to send fax to an email address.
You can attach an analogue adaptor and a physical fax on the voip line.