Hi. You can use for exemple FaxTools Expert, availlable in the Marketplace. 

http://www.softcity.com/en/product/show.php?&id_language=1&fonction=show&id_product=114&id_subCategory=&platform=windows&id_os=

Benoit,

You can send and even receive fax without any hardware or modem. You can subscribe to a service and send fax throw a web portal.

How it works basically, one you have taken the subscription, (generally around 10$ a month), you connect to a web page with your credentials, and sending a fax is as simple as giving the fax number of your correspondent and uploading the documents (generally : pdf, word, tiff formats are supported), and that's it. After processing your fax, the server send you a mail with the result, if the fax has or hasn't been sent.

For my own, I use www.myfax.com to send faxes, and event to receive faxs, as they provided me a fax number , and as we have redirected our office fax to this number. Then, few faxs I received are coming in my mail inbox, in pdf format.

Myfax

FaxTools is my reference in this domain, you can just drop your old Fax to the garbage.

Definitely FaxTools Expert !

Faxtools is the best product to manage your fax on your PC. If your provider is Free, Free offer you the possibility to send fax with PDF file.

I agree with above comments: FAXTOOLS will allow you to email all your documents to a fax machine and also get faxes you receive directly into your Email Inbox

For receiving faxes I have a personal number provided by my ISP which is very handy – there is no charge as the sender is charged a little extra for the call.

If your company needs a sending and receiving fax solution then have a look at RightFax (Open Text Fax Server) from http://www.processflows.co.uk/rightfax as this will integrate into Exchange or Notes plus stacks of other technologies (MOSS, Oracle, SAP, etc).

Do anybody use WinFax Pro (http://www.symantecstore.com/antivirus/winfax-pro-f.htm)?

@Xu Cao : I used it in the 90's including putting in the (very unstable) network version into a customer. I understood that Symantec dropped it in 2006. I think a third party offers support for it if you still use it.

Very good info - Thank you Paul!

No one mentioned that Skype has an option to send faxes. If you have Skype credit I believe you can use it to pay for the faxes.