You don't specifically need to purchase fax server software anymore. There are now web services available that let you "email" your faxes.
Such as:
http://www.utbox.net/
You send an email, the service converts the email to a fax and then faxes your customers or suppliers.
If you set-up an account with them (the trial is free) you're paying 15c per page for faxing and a relatively low 3, 6 or 12 month fee. i.e., $19.95 for 3 months "line rental".
As far as CAPITAL is concerned, you still either click on "Fax" or "Email" and get different pop-up boxes. One emails directly to the customer, the other sends the email to the web service which converts your email to a fax and faxes it onto your target. You need to do a little set-up on the CAPITAL side to make this work, but the set-up is very simple. Refer to our technical bulletins section for more details.