The following section covers more involved topics such as mail configuration and setting up mail for your entire domain.
Out of the box, you should be able to send email to external
hosts as long as you have set up
/etc/resolv.conf
or are running your own
name server. If you would like to have mail for your host
delivered to the MTA (e.g., sendmail) on your own FreeBSD host, there are two methods:
Run your own name server and have your own domain. For
example, FreeBSD.org
Get mail delivered directly to your host. This is done by
delivering mail directly to the current DNS name for your
machine. For example, example.FreeBSD.org
.
Regardless of which of the above you choose, in order to have mail delivered directly to your host, it must have a permanent static IP address (not a dynamic address, as with most PPP dial-up configurations). If you are behind a firewall, it must pass SMTP traffic on to you. If you want to receive mail directly at your host, you need to be sure of either of two things:
Either of the above will allow you to receive mail directly at your host.
Try this:
#
hostname
example.FreeBSD.org#
host example.FreeBSD.org
example.FreeBSD.org has address 204.216.27.XX
If that is what you see, mail directly to
<yourlogin@example.FreeBSD.org>
should work without
problems (assuming sendmail is
running correctly on example.FreeBSD.org
).
If instead you see something like this:
#
host example.FreeBSD.org
example.FreeBSD.org has address 204.216.27.XX example.FreeBSD.org mail is handled (pri=10) by hub.FreeBSD.org
All mail sent to your host (example.FreeBSD.org
) will end up being
collected on hub
under the same username instead
of being sent directly to your host.
The above information is handled by your DNS server. The DNS record that carries mail routing information is the Mail eXchange entry. If no MX record exists, mail will be delivered directly to the host by way of its IP address.
The MX entry for freefall.FreeBSD.org
at one time looked like
this:
freefall MX 30 mail.crl.net freefall MX 40 agora.rdrop.com freefall MX 10 freefall.FreeBSD.org freefall MX 20 who.cdrom.com
As you can see, freefall
had many MX entries.
The lowest MX number is the host that receives mail directly if
available; if it is not accessible for some reason, the others
(sometimes called „backup MXes”) accept messages
temporarily, and pass it along when a lower-numbered host becomes
available, eventually to the lowest-numbered host.
Alternate MX sites should have separate Internet connections from your own in order to be most useful. Your ISP or another friendly site should have no problem providing this service for you.
In order to set up a „mailhost” (a.k.a. mail
server) you need to have any mail sent to various workstations
directed to it. Basically, you want to „claim” any
mail for any hostname in your domain (in this case *.FreeBSD.org
) and divert it to your mail
server so your users can receive their mail on
the master mail server.
To make life easiest, a user account with the same username should exist on both machines. Use adduser(8) to do this.
The mailhost you will be using must be the designated mail exchanger for each workstation on the network. This is done in your DNS configuration like so:
example.FreeBSD.org A 204.216.27.XX ; Workstation MX 10 hub.FreeBSD.org ; Mailhost
This will redirect mail for the workstation to the mailhost no matter where the A record points. The mail is sent to the MX host.
You cannot do this yourself unless you are running a DNS server. If you are not, or cannot run your own DNS server, talk to your ISP or whoever provides your DNS.
If you are doing virtual email hosting, the following
information will come in handy. For this example, we
will assume you have a customer with his own domain, in this
case customer1.org
, and you want
all the mail for customer1.org
sent to your mailhost, mail.myhost.com
. The entry in your DNS
should look like this:
customer1.org MX 10 mail.myhost.com
You do not need an A record for customer1.org
if you only
want to handle email for that domain.
Be aware that pinging customer1.org
will not work unless
an A record exists for it.
The last thing that you must do is tell sendmail on your mailhost what domains and/or hostnames it should be accepting mail for. There are a few different ways this can be done. Either of the following will work:
Add the hosts to your
/etc/mail/local-host-names
file if you are using the
FEATURE(use_cw_file)
. If you are using
a version of sendmail earlier than 8.10, the file is
/etc/sendmail.cw
.
Add a Cwyour.host.com
line to your
/etc/sendmail.cf
or
/etc/mail/sendmail.cf
if you are using
sendmail 8.10 or higher.
All FreeBSD documents are available for download at http://ftp.FreeBSD.org/pub/FreeBSD/doc/
Questions that are not answered by the
documentation may be
sent to <freebsd-questions@FreeBSD.org>.
Send questions about this document to <freebsd-doc@FreeBSD.org>.