I run a hobby server on a Comcast residential connection.  
 
A number of years ago, I noticed larger organizations (Gmail, etc) began
rejecting email from dynamic ip.  The solution was a "smart host" to
relay email.  Comcast would accept connections on port 25 and forward
from their well-know (unblocked) ip address.  Here's the line I added to
/etc/postfix/main.cf that made it work.
 
    relayhost = smtp.comcast.net
 
Last year, there was discussion on this list about Comcast blocking port
25.  I was unaffected at that time.  
http://archives.mn-linux.org/pipermail/tclug-list/2009-February/thread.h
tml 
 
However, last month on or after Feb 8, 2010,  Comcast stopped accepting
my port 25 connections.  
 
    $ telnet smtp.comcast.net 25
    Trying 76.96.30.117...
    telnet: Unable to connect to remote host: Connection timed out
 
I called Comcast and they said "that's right, use port 587."    I can
telnet to port 587 , but I believe this requires authentication,
presumably with my Comcast credentials.  
 
I've reconfigure postfix for port 587 per 
http://www.kclug.org/pipermail/kclug/2008-February/032558.html 
 
and setup SMTP Authentication per 
http://www.freelock.com/kb/postfix-relayhost 
but I'm stuck on the last step:
 
     # urpmi --media main libsasl2-plug-login libsasl2-plug-plain
    bash: urpmi: command not found
 
Can someone supply the magical apt-get incantation to get me started?
 
I'm running postfix 2.3.8 on Debian and can live with only out-going
mail.  
 
 
 
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