# Postfix setup on a laptop.


> older article that I've revived.

# Problem
The problem: you have a laptop and you're not always connected to the Internet. Still
you want to sent mail even when you're offline. You cannot use just any mail server
out there, 'cause a lot of them don't relay. So you must use your own mail server.
<p>
You'll need:
<ol>
<li>postfix, only used for queuing and forwarding the mail
<li>openSSH, for setting up a tunnel
</ol>

 OpenSSH config
You will need to create a ssh tunnel to your mail server. This is
the command I use:

    ssh -2 -N -f -L 10025:elektron.atoom.net:25 miekg@elektron.atoom.net 2>/dev/null

Of course you also want to setup ssh so that you can login without typing a password.

 postfix config
Next you must tell postfix to use you're tunnel. It is also important
to keep postfix from doing MX lookups. In the main.cf of postfix add
the following:

    relayhost = [127.0.0.1]:10025   # use the tunnel, no MX lookups
    defer_transports = smtp               # only send when online
    mydestination = localhost.localdomain   # not sure if this is needed

 system config
Put the startup commands in `/etc/dhclient-exit-hooks`. This way every time
you get a IP number from a dhcp-server the tunnel is re-established and the mail is
flushed,  `/etc/dhclient-exit-hooks`:

    # start an ssh tunnel to elektron
    ssh -2 -N -f -L 10025:elektron.atoom.net:25 miekg@elektron.atoom.net 2>/dev/null

    # run the mailqueue
    /usr/sbin/sendmail -q

Also make a cronjob that runs every now and then to flush the queue:

    # run queue every 5 minutes
    */5 * * * *     root  test -x /usr/sbin/sendmail && \ 
    nice -n10 /usr/sbin/sendmail -q

That's it. Mail should now be queued until it can be delivered via you're own mail
server.