[lug] Sending e-Mail under Linux

[rm at fabula.de]

On Thu, Aug 29, 2002 at 08:04:39AM -0600, Jeff Schroeder wrote:
> 
> That's because you've logged into the system as user "john", and your 
> hostname (by default) is "localhost.localdomain".  When you clicked 
> "send" in KMail, it used your local copy of Sendmail to fire off the 
> letter.  Sendmail resolved the Hotmail domain and successfully 
> delivered the message.
> 
> Note that replying to that message will fail, because Hotmail (and, 
> indeed, anyone "out there") won't be able to resolve 
> "localhost.localdomain" properly.  It'll resolve to their own machine, 
> if anything at all.

O, and that's a very convenient thing: whenever an anoying webpage
asks you for your email address: enter root at 127.0.0.1 , then all
their spam will go to their sysadmin ;-)

> > 2.  After playing with KMail a little, I found that I could change
> > the identity to simulate my wife's yahoo account, and even send an
> > e-mail to a list she belongs to.  I don't understand how I managed to
> > do this without some sort of authentication stopping me.  It seems
> > like I could simulate anyone I wanted?
> 
> Absolutely.  Welcome to the world of spammers. ;)
> 
> While you can "impersonate" anyone by changing your From: or Reply-to: 
> addresses, remember that when someone responds to your message, it will 
> go to the address you've given.  So in this case, your wife will get 
> the responses-- not you.

While we are on this topic: while it's very easy to "impersonate" and 
fool the fool, it's actually pretty hard to fool a proper sysadmin --
if you look at the heade of the 'fake' mail you sent (you might need
to change the settings of you mail reader to see _all_ headers) you'll
see something like:

	Received: from gate.mh-freiburg.de (unknown [192.168.20.1])
		by forte.mh-freiburg.de (Postfix) with ESMTP
		id 42FA01B32F3; Thu, 29 Aug 2002 10:55:04 +0200 (MEST)
	Received: from wesley.informatik.uni-freiburg.de
	+(wesley.informatik.uni-freiburg.de [132.230.153.50])
		by gate.mh-freiburg.de (Postfix) with ESMTP
		id 6DBD37FBD; Thu, 29 Aug 2002 11:12:20 +0200 

 all transfering servers will leave a trace in the mail header, the last
on in the list will be your server, and most likelyy with its IP-Address,
so one _can_ actually trace back who (what system) did sent the mail.

[...]
> IMHO, e-mail is anything but amateurish.  There's a lot of stuff to 
> learn, and these are good questions to start with.  Hopefully you'll be 
> able to set everything up properly, and enjoy KMail (it's my mail 
> program of choice too).

Indeed, in some countries the sendmail book is considered a lethal
weapon ;-)

  Ralf

> HTH,
> Jeff
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