Is Email a Viable Alternative to Faxing Documents?

“Instead of a fax machine, if a document is scanned and saved can it simply be attached to an email and sent rather than using an online fax service? Providing, of course, that you have the email address for the destination of the document.”
Emailing documents is definitely a viable option for replacing a fax, although there may be reasons why you would want to fax a document instead.

Company Policies on Faxing vs. Email
Many companies maintain policies stating fax is the only recognized alternative to a signature on a document sent by mail or private courier. Because faxing documents has been around longer, companies are more comfortable with accepting a signature on a document received via fax, even though sending the document via email gets the same result.
Information Security
Most email is sent as clear text with no encryption. This means if you include a credit card number (or other personal information) in an email message it’s possible someone other than the person you sent it to might read it. With a fax, as long as you dial the correct number your fax should end up being read only by the intended recipient. A couple ways around this would be to either send the file in an encrypted email message or to send the file in an encrypted zip file attached to standard email message.
For non-sensitive documents email could easily replace faxing. You may remain at the mercy of policies put in place either by the company you work for or by a company you need to send a fax to. An interim step generally accepted by all companies would be to use an online fax service. I currently subscribe to MyFax for my own faxing needs.