title_body: Calibre can optionally use a server to send mail I tried calibre share/send to, but it failed with:
  
  Sending failed...
  
  Traceback (most recent call last):
    File "/usr/lib/calibre/calibre/gui2/email.py", line 44, in run
      self.func(*self.args)
  
  
  I was just curious, really, how calibre sends to my Kindle account because I don't recall authorizing it, nor do I see sent messages from it.  (Not that I configured it with my e-mail settings.)
  
  Does Amazon just "trust" the calibre software?  if so, good.  Curious.
  
  Yes, I suppose I could go look in the above python script...
upvoted_answer: Calibre uses the address that was entered in the Sharing books by email dialog box. Apparently, the developer didn't anticipate that someone would try to use send without configuring email settings. 
  
  You might want to contact him and let him know about this issue. (He usually fixes problems the very same day.)