The Sendmail mail server is - with
an estimated 100 million users each day - without a doubt the most widely
used mail server on the Internet. So why use Postfix?
Here is a quote that may shed some light upon this:
"The Sendmail configuration file is one of
those files that looks like someone beat their head on the keyboard. After
working with it... I can see why!" (Harry Skelton)
Postfix aims to be "fast, easy to administer, and secure,
while at the same time being Sendmail compatible enough to not upset existing
users". And it's quite good at this.
If you want Sendmail anyway, you can still install it from your Mandrake
Linux CD with urpmi sendmail, you should uninstall Postfix first,
of course. You can save yourself a lot of trouble by using the install-sendmail
script (this will also configure fetchmail for you). If you need a complex
Sendmail setup, use 'webmin'.
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The configuration file is '/etc/postfix/main.cf', the
configuration process is explained in /usr/share/doc/postfix-[...]/html/basic.html'.
Postfix is excellently documented. Changes in the configuration must
be followed by this command:
service postfix reload
issued by 'root'.
In order to work properly, Postfix has to run on a machine
with a fully qualified domain name (FQDN), i.e. a name in the form of 'xxxxxx.yyyy.zzz',
a simple name will not do. Run the
hostname
command in order to find out if your machine fulfills
this requirement.
If your machine does not have a FQDN, you have to assign
one to it, e.g. by using 'draknet' from the Mandrake Control Center, or
by hand editing '/etc/hosts' (only for static IPs) and '/etc/sysconfig/network'.
Configure your mail program to use your mail server.
This is usually done in a configuration dialog called 'SMTP' or 'Send'. Most
programs provide the opportunity to switch to 'Sendmail', which is perfectly
OK, since Postfix is compatible to it. If you have to specify the path to
the server's executable, use '/usr/sbin/sendmail'. Do not configure any options
that might be available, you will do this in 'main.cf'. You might want to
set your mail-address (the string that appears in 'From:'), though. This
is easier to do in the client than at the server.
This method has the advantage that it leaves the actual
delivering of the mail to a server which is connected permanently to the
Internet. This server has a better chance to deliver mail to servers which
are hard to reach or are temporarily disconnected.
The disadvantage is that you usually have to use the mail-address given to
you by your provider. Most providers do not allow relaying mail using a self-made
sender-address.
Add this line to 'main.cf':
relayhost = [mail.provider.com]
[mail.provider.com] is the name or IP address of your
provider's SMTP server.
Edit '/etc/postfix/aliases' and change the second field
of the last line (" Person who should get root's mail") to your user account.
Now build 'aliases.db' with
postalias /etc/postfix/aliases
If you use Dial-On-Demand, you want to prevent Postfix
from delivering mail if you do not explicitly tell it to do so. Add this
line to 'main.cf':
defer_transports = smtp
If your machine is part of a local network which doesn't
provide DNS, you should turn off DNS lookups:
disable_dns_lookups = yes
To get the mail out every time you connect to the Internet,
create the file 'ip-up.local' in '/etc/ppp' and put these lines in it:
#!/bin/bash
/usr/sbin/sendmail -q
Save and run chmod +x /etc/ppp/ip-up.local
to make the file executable.
If your machine gets its IP via DHCP, you might encounter
some trouble with bouncing mails from your relay host (553, 'domain doesn't
exist'). In this case you have to tell Postfix to strip the machine name
from outgoing mails by removing the hash (#) in front of this line in 'main.cf':
myorigin = $mydomain
Restart Postfix after changing 'main.cf' and try again.
This method allows you to use a self-made 'from:' address
in any case. You should be connected to the Internet quite often to allow
Postfix delivering deferred mail (i.e. mail which couldn't be delivered at
the first try). Your mail agent should include a 'reply-to' address for an
external POP-account, unless you use a more sophisticated setup as described
in scenario 3.
You don't have to edit 'main.cf', unless having to comply
to certain circumstances mentioned in Scenario 1. Just edit 'aliases' and
build 'aliases.db'.
This is a nice method to impress your friends ;-). It
requires some effort, though:
- Register your domain name via a
free domain parking service.
- Find a web-space provider which offers SMTP. This
is the hard part. I'm using Westhost:
low prices, support OK, servers running on GNU/Linux, Debian I think. (No,
I don't get money for mentioning them ;-)).
- Transfer your domain name from the domain parking
service to your new web-space account. This usually just takes a mail to
the parking service where you tell them the DNS addresses of your web-space
provider.
The next step is to configure your machine. You'll have
to change the hostname by editing '/etc/HOSTNAME', '/etc/hosts.conf' and '/etc/sysconfig/network'.
The hostname must be an FQDN, consisting of three parts: [machine name].[domain
name].[toplevel domain]. Use the domain name and top-level domain
you've registered. You can use any machine name you like, but you should
refrain from using "www", since your web-account already uses that one.
Having made the changes, restart the network service
with/etc/rc.d/init.d/network restart. If everything went fine,
hostname --fqdn should show you the FQDN of
your machine.
Now configure Postfix: remove the hash-sign (#) in front
of these lines in 'main.cf':
myorigin = $mydomain This will strip
the machine name fromall mail.inet_interfaces = $myhostname, localhost
This makes Postfix listen only on specified network interfaces.mynetworks = 192.168.0.0/28, 127.0.0.0/8
You have to adapt the first IP to the one you've assigned to your machine
name in /etc/hosts. '192.168.0.0/28' however is a sure bet, since it is a
valid address for local networks.
Edit 'aliases' in /etc/postfix' and build 'aliases.db'
withpostaliases /etc/postfix/aliases. Add further parameters
if necessary (described in Scenario 1) and restart Postfix by using the 'reload'
command.
Ready! :-).
If you are using this method with a variable IP, there's
one huge drawback: sooner or later you will find that more and more sites
begin to reject your mail. Welcome to the DUL, the Dial-up User
List! This list is used by many servers to block mail from mail servers with
non-static IPs. Some people obviously have way too much time on their hands
(yes, they blacklisted me too :-(().
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Now it's time for a test. Your email address is [your
user name]@[your machine's FQDN], but for sending mail locally, you
just have to provide [username]@localhost.
On a virtual terminal, type mail -s test [your username]@localhost.
On the next line, hit CTRL and 'd'. Hit ENTER on the Cc: prompt. mail
will complain about the missing body, but that's OK.
Now type mail and you should see the 'test' message in your mailbox.
Bingo! ;-)
If you do not see it there, quit mail with q and
runmailq. This will show queued mail along with status reports
(e.g. error messages).
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 Configuring Fetchmail
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