Internet fax
Another thing that you should be looking at closely when considering using any kind of internet fax service provider is the format in which the documents will be sent to you. Generally most providers will send the faxes they receive for you as TIFF attachments but unfortunately not everybody will have the capability on their machines to open such documents. Therefore if you can look for a company that will deliver these faxes to you in a variety of different formats and which are compatible with the office tools you currently have on your machine.
If you keep the above pointers in mind when looking for an internet fax you should be able to find one who meets your particular requirements and needs perfectly.