Question: how to send a fax to an efax number?
Answer: Create a new email message.
In the "To:" field, enter the recipient's fax number followed by @efaxsend.com. For example: ... 
Attach the file(s) (10 maximum) you would like to send as a fax. To include a cover page, type the text in the body of the email message. ... 
Click Send.