Posted on Wednesday, 19th January 2011 by admin
Sendmail mail server setup and configuration step by step.
Let’s start and setup our first sendmail server.
First thing to do is install the packages that we need.
yum install sendmail sendmail-cf
Then edit the sendmail.mc file and make those changes above.
Find the line:
dnl define(`confAUTH_OPTIONS’, `A p’)dnl
and change it to:
define(`confAUTH_OPTIONS’, `A p’)dnl
Then change those lines above. This is need to get outlook express and Mozilla to work with plain text authentication.
Use it only in a secure local network, otherwise use a different authentication mechanism for example ssl.
From this:
dnl TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN’)dnl
dnl define(`confAUTH_MECHANISMS’, `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN’)dnl
To this:
TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN’)dnl
define(`confAUTH_MECHANISMS’, `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN’)dnl
Next step is change the queue parts for fine tuning from these:
dnl define(`confTO_QUEUEWARN’, `4h’)dnl
dnl define(`confTO_QUEUERETURN’, `5d’)dnl
dnl define(`confQUEUE_LA’, `12′)dnl
dnl define(`confREFUSE_LA’, `18′)dnl
To these:
define(`confTO_QUEUEWARN’, `4h’)dnl
define(`confTO_QUEUERETURN’, `5d’)dnl
define(`confQUEUE_LA’, `12′)dnl
define(`confREFUSE_LA’, `18′)dnl
Next thing is the maximum children numbers:
dnl define(`confMAX_DAEMON_CHILDREN’, `20′)dnl
To:
define(`confMAX_DAEMON_CHILDREN’, `20′)dnl
Then the maximum connection number per IP address from this:
dnl define(`confCONNECTION_RATE_THROTTLE’, `3′)dnl
To this:
define(`confCONNECTION_RATE_THROTTLE’, `3′)dnl
Next is the local daemon copy the line and insert your server’s IP address:
DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA’)dnl
DAEMON_OPTIONS(`Port=smtp,Addr=192.168.0.40, Name=MTA’)dnl
If you are using public IP address then put that instead of the private one.
If you want to get IPv6 support then uncomment this line:
dnl DAEMON_OPTIONS(`port=smtp,Addr=::1, Name=MTA-v6, Family=inet6′)dnl
To this:
DAEMON_OPTIONS(`port=smtp,Addr=::1, Name=MTA-v6, Family=inet6′)dnl
Obvious the Address part should be filled properly.
Next find the line:
dnl FEATURE(`relay_based_on_MX’)dnl
and change this to:
FEATURE(`relay_based_on_MX’)dnl
If your server runs on a DSL or cable connection then you need to change the smart host part too:
define(`SMART_HOST’, `smtp.ntlworld.com’)dnl
Obvious change the smtp.ntlworld.com part to your provider. Then your server will be able to communicate through smtp protocol.
Save the sendmail.mc file, this part is done.
Next thing to do is edit the access file and insert your server’s IP address like this:
Connect:192.168.0.40 RELAY
Connect:192.168.0 RELAY
Change the addresses to your server’s IP address and for your local network address too.
The second line needs for the clients computers on your network to be able to relay with the server.
If you are using public IP address then put that IP instead of the private one.
This file enables the sendmail server to reject and accept domain(s) and IP addresses.
When this done you need to hash the access file with this command:
makemap hash /etc/mail/access.db < /etc/mail/access
Next thing to do is enter the domain name(s) that you have into the local-host-name file like this:
vi /etc/mail/local-host-names
opensourcetechnology.co.uk
mylovelydomainname.com
mythirddomainname.com
Then save the file and close it.
Create a test user for this email account:
useradd –s /sbin/nologin test1
Change the password for the test1 user:
passwd test1
Then edit the aliases file under the /etc directory and put these line into it:
test1: test1
Save and close it then issue the newaliases command:
newaliases
/etc/aliases: 78 aliases, longest 10 bytes, 781 bytes total
After this you got a test1@opensourcetechnology.co.uk email address.
If you want more addresses for this account just edit the /etc/aliases file and save it.
Then issue the newaliases command to be accept the new lines from the aliases file.
We are finished with the sendmail part. Let’s compile the sendmail and start it.
make clean
make all
make restart
You can start any service in CentOS Linux with these commands:
service sendmail start
or
/etc/init.d/sendmail start
Check the sendmail service because it should be switched on otherwise the next reboot the servcie wont start with the chkconfig command:
chkconfig sendmail on
Be carefull with postfix, exim and any another mail servers. Only one mail server can run on the 25 smtp port. So check the service to be switched off with the command:
chkconfig postfix off
chkconfig exim off
And check the firewall smtp port that should be enabled. You can check this with iptbales command:
iptables -L
If it says “ACCEPT tcp – anywhere anywhere state NEW tcp dpt:smtp” that is fine.
Last thing to do is change the server name for the appropriate one.
Go to /etc/sysconfig and edit the network file.
vi /etc/sysconfig/network
Change this:
HOSTNAME=localhost.localdomain
To:
HOSTNAME=mail.opensourcetechnology.co.uk
That’s it we are done. After this you should restart the server otherwise the server name wont change.
Before that save every open files!!!
You can restart the server with this command:
shutdown -r now (-r means restart the box. If you put -h the server wont restart it will stay in halt state)
After you rebooted the server test the sendmail server with this command:
telnet localhost 25
###################
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
220 mail.opensourcetechnology.co.uk ESMTP Sendmail 8.13.8/8.13.8; Sun, 16 Jan 2011 19:14:03 GMT
helo me
250 mail.opensourcetechnology.co.uk Hello localhost.localdomain [127.0.0.1], pleased to meet you
mail from:lszabo@opensourcetechnology.co.uk
250 2.1.0 lszabo@opensourcetechnology.co.uk… Sender ok
rcpt to:test1
250 2.1.5 test1… Recipient ok
data
354 Enter mail, end with “.” on a line by itself
subject:test
test
.
250 2.0.0 p0GJE39C006422 Message accepted for delivery
quit
##################
To check the open ports on your box use the nmap command.
nmap localhost
nmap 192.168.0.40
nmap myexternalipaddress
Hints for DSL/Broadband connections:
If your server is behind a firewall don’t forget to forward the 25 (smtp) port into your box.
On few DSL line you might have a problem with the MTU size. If the mails stuck into the Linux box then change the MTU size to 1420 in your router.
The DSL line is not a real Ethernet network. It is a pppoe (<a href=”http://en.wikipedia.org/wiki/Point-to-Point_Protocol_over_Ethernet”>http://en.wikipedia.org/wiki/Point-to-Point_Protocol_over_Ethernet</a>) line so the MTU size is smaller then a real Ethernet and it can cause trouble for sendmail.
So if you are having this kind of problem(mail can’t go out from the box) try to change this in the router and in the Linux box too.
In the Linux box the MTU size at the /etc/sysconfig/networking/devices/ifcfg-eth0
You can download all the configuration files from here:
sendmail.mc
local-host-names
access
Sendmail-Doc
Next blog will be about the Dovecot POP3/IMAP server.
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