mail server in linux

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Configure Host Name Lookup in RHEL/CentOS 5

Before starting to use Red Hat Enterprise Linux 5 or CentOS 5, the static host name table lookup file /etc/hosts must

be corrected first. The steps below describes how to do this.

Configure Host

1. ClickApplications, selectSystem Tools then clickFile Browser. This will launch the File Browser window.
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2. In theLocation field, type in/etc and press Enter. If you dont see the Location field, click the notepad button to

toggle to text-based location bar.

3. Locate and double click on the file hosts to open it for editing. Update the content similar to the lines below.

127.0.0.1 localhost.localdomain localhost

::1 localhost6.localdomain6 localhost6

192.168.0.4 mail.acme.local mail
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Replace the last line with your ownIP address,fully qualified domain name and host name.

Test the Host Name Lookup

1. ClickApplications, selectAccessories, and clickTerminal. This will launch the Terminal window.
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2. In the terminal window, type in the command below.

ping localhost

You should see localhost.localdomain and 127.0.0.1

3. Next, type in the command below.

ping mail

Replace mailwith your own hostname. You should see your fully qualified domain name and ip address.

Postfix SMTP Server Setup Howto for RHEL/CentOS 5

Installing and setting up Postfix SMTP Server in Red Hat Enterprise Linux 5 or CentOS 5 is easy. Postfix has secure

default settings so we just need to open it up a bit.

Install Postfix and Mail Transport Agent Switcher
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1. If you did not add postfix and system-switch-mail-gnome during the CentOS installation, you can add it now

using Package Managertool.

Switch to Postfix from Sendmail:

By default, Sendmail is the active SMTP server. Heres how to change it.
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1. ClickSystem,

selectAdministration, and clickMail Transport Agent Switcher. This will launch the system-switch-mailwindow.

2. In the system-

switch-mail window, selectPostfixand clickOk.

Configure Postfix
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1. ClickApplications,

selectSystem Tools then clickFile Browser. This will launch the File Browser window.

2. In

theLocation field, type in/etc/postfixand press Enter. If you dont see the Location field, click the notepad button to

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3. Double click on the

file main.cfto open it for editing. We need to make it listen to network request, accept mails bound to our domain and

usemaildirwhich is a better mailbox format than mbox the default.

Find the following keys and change its values as follows

inet_interfaces = all

mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain

home_mailbox = Maildir/

In main.cf, lines starting with # are comments. Save the file after completing your changes.

Make sure that all mail_spool_directory lines are commented out. Otherwise, it will override the

setting in the home_mailbox line above.
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4. Restart the postfix service.Learn how to restart services here.

Test Postfix

1. ClickApplications,

selectAccessories, and clickTerminal. This will launch the Terminal window.
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2. In

the Terminal window, type in the highlighted commands below.

Sample postfix session. Replacejohndoe with any valid user account. The dot after the line test is a command that

should be typed in.

If you need to add new user accounts,learn how to add or remove user accounts here.

[root@mail ~]# telnet localhost smtp

Trying 127.0.0.1...

Connected to localhost.localdomain (127.0.0.1).

Escape character is '^]'.

220 mail.acme.local ESMTP Postfix

ehlo localhost

250-mail.acme.local

250-PIPELINING

250-SIZE 10240000

250-VRFY

250-ETRN

250-ENHANCEDSTATUSCODES

250-8BITMIME

250 DSN

mail from:

250 2.1.0 Ok

rcpt to:

250 2.1.5 Ok

data
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354 End data with .

test

.

250 2.0.0 Ok: queued as 9729067C17

quit

221 2.0.0 Bye

Connection closed by foreign host.

[root@mail ~]#

To check if the mail indeed exists

[root@mail ~]# cd /home/johndoe/Maildir/new

[root@mail new]# ls

1185669817.Vfd00I18012M795756.mail.acme.local

[root@mail new]# cat 1185669817.Vfd00I18012M795756.mail.acme.local

Dont worry, you dont have to type in the whole filename above. Just type in the first few characters say118 then

press Tab to activate automatic completion.

From [email protected] Thu Feb 22 21:48:28 2007

Return-Path:

X-Original-To: johndoe

Delivered-To: [email protected]

Received: from localhost.localdomain (localhost.localdomain [127.0.0.1])

by mail.acme.local (Postfix) with SMTP id 9729067C17

for ; Thu, 22 Feb 2007 21:48:26 -0500 (EST)

Message-Id:

Date: Thu, 22 Feb 2007 21:48:26 -0500 (EST)

From: [email protected]

To: undisclosed-recipients:;

test

[root@mail mail]#

If you encounter any problems, check the log file at/var/log/maillog.

Review yourPostfix aliases configuration file. There are some predefined email aliases that might conflict with

your existing mail accounts like sales, marketing, info, etc.

How to Add or Remove User Accounts in RHEL/CentOS 5

In Linux, new user accounts automatically receive mail accounts. Here are the steps for adding a new user account in

Red Hat Enterprise Linux 5 and its derivative CentOS 5.

Manage User and Group Accounts (GUI)
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This section describes how to use the User Manager to manage the user and group accounts.

1. ClickApplications then selectSystem Settings and clickUsers and Groups. This will launch the User

Manager window.
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2. In the User Manager window, clickAdd User. This will show the Create New User window.

3. In the Create New User window, fill in the User Name,Full Name,Passwordand Confirm Password.

ClickOk when youre done.

To avoid user account related problems, do not use uppercase letters when creating user names.
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4. Thats it, you have just created a new user. To remove a user, select the user you want to remove and clickDelete.

Manage User and Group Accounts (Console)

Below are the console commands to manage the user and group accounts. Type in any of the commands below

without any parameter to see that commands help information.

/usr/sbin/useradd [options] login_name

creates a new user

/usr/sbin/usermod [options] login_name

modifies a users attributes

/usr/sbin/userdel [options] login_name

deletes the specified user. Use the -roption to automatically remove the users home directory and mail spool.

/usr/bin/passwd login_name

sets the password for the specified user

/usr/sbin/groupadd [options] group_name

creates a new group

/usr/sbin/groupmod [options] group_namemodifies a groups attributes

/usr/sbin/groupdel group_name

deletes the specified group

Setup of user password Expiration:
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1.

ClickApplications then selectSystem Settings and clickUsers and Groups. This will launch the User

Manager window.

2. Select the user you wish to configure and clickProperties.
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3. In the User Properties windows, click thePassword Info tab.

4. Check theEnable Password Expiration checkbox to enable password expiration. The list below describes the

available settings.

Days before change allowed

Number of days from the last password change to allow another password change.
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Days before change required

Number of days from the last password change to require another password change.

Days warning before change

Number of days before the expiry of the password to notify the user.

Days before account inactive

Number of inactive days after the expiry of the password to deactivate the account. 0 means

do not deactivate.

You can also do this from the command line, below are the equivalent commands.

chage login_name

modifies the password expiry information of the specified login name. You need root access to use this command.

chage -l login_name

shows the password expiry information of the specified login name

chage

displays the help information

You can notify the users with expiring password via email using the checkpwexpire script. Copy the script into

the/etc/cron.daily and give it execute permission so it will automatically run every day.

Dovecot POP3/IMAP Server Setup Howto for RHEL/CentOS 5

Installing and setting up Dovecot in Red Hat Enterprise Linux 5 or CentOS 5 is easy. All we have to do is to enable the

services we would like to provide and we are good to go.

Install Dovecot
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1. If you did not add dovecot during the CentOS installation, you can add it now using Package Manager.

Configure Dovecot

1. ClickApplications, selectSystem Tools then clickFile Browser. This will launch the File Browser window.
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2. In theLocation field, type in/etc and press Enter. If you dont see the Location field, click the notepad button to


3. Double click on the file dovecot.confto open it for editing. We need to change a few key items.

Find the following keys and change its values as follows
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protocols = pop3 pop3s imap imaps

mail_location = maildir:~/Maildir/

pop3_uidl_format = %08Xu%08Xv

imap_client_workarounds = delay-newmail outlook-idle netscape-eoh

pop3_client_workarounds = outlook-no-nuls oe-ns-eoh

For 64-bit users: Add the line login_process_size = 64 in the file/etc/dovecot.conf.

Lines starting with # are comments. The last two line enables workarounds for various client bugs. Save the file after

completing your changes.

4. Start the dovecot service.Learn how to start and stop services here.

Test Dovecot
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1. ClickApplications, selectAccessories, and clickTerminal. This will launch the Terminal window.

2. In the Terminal window, type in the highlighted commands below.

Sample dovecot session. Replacejohndoe and password with any valid user name and password.
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[root@mail ~]# telnet localhost pop3

+OK dovecot ready.

user johndoe

+OK

pass password

+OK Logged in.

list

+OK 1 messages:1 622

.

retr 1

+OK 622 octets

Return-Path:

X-Original-To: johndoe

Delivered-To: [email protected]

Received: from localhost.localdomain (localhost.localdomain [127.0.0.1])

by mail.acme.local (Postfix) with SMTP id 9729067C17

for ; Thu, 22 Feb 2007 09:06:37 -0500 (EST)

Message-Id: Date: Thu, 22 Feb 2007 09:06:37 -0500 (EST)

From: [email protected]

To: undisclosed-recipients:;

X-IMAPbase: 1172153557 1

Status: O

X-UID: 1

Content-Length: 5

X-Keywords:

test

.

quit

+OK Logging out.


[root@mail ~]#


Postfix SMTP Authentication and Dovecot SASL

SMTP Authentication (SMTP Auth) provides an access control mechanism that can be used to allow legitimate

users to relay mail while denying relay service to unauthorized users, such as spammers.

Thanks to the new SASL support in Dovecot 1.0 and the new Dovecot SASL support in Postfix 2.3, setting up SMTP

authentication is now easier. Instead of setting up two separate authentication for Postfix and Dovecot, we can now

just setup the authentication in Dovecot and just let Postfix talk to Dovecot.
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Configure Postfix and Dovecot

1. Edit the file/etc/dovecot.confand make sure your auth defaultsection has the lines below.

auth default {

socket listen {

client {

path = /var/spool/postfix/private/auth

mode = 0660user = postfix

group = postfix

}

}

mechanisms = plain login

}
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2.

Edit/etc/postfix/main.cf, find the keys below and change its values as follows or add it at the bottom of the file if the

key (the word before the = sign) cannot be found.

mynetworks = 127.0.0.0/8

smtpd_sasl_type = dovecot

smtpd_sasl_path = private/auth

smtpd_sasl_auth_enable = yes

smtpd_recipient_restrictions = permit_mynetworks,

permit_sasl_authenticated, reject_unauth_destinationbroken_sasl_auth_clients = yes

The first line says trust only localhost, meaning only localhost can send email outside the network (relay). The last

line is there to support old clients like Microsoft Outlook Express 4.0 and Microsoft Exchange 5.0 just in case

someone is still using it.

Lines starting with # are comments. Save the file after completing your changes.
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3.

Restart the Dovecot and Postfix service. But if you installed MailScanner, restart MailScanner instead of Postfix.

Test Postfix

In

a Terminal window, type in the highlighted commands below.

Sample postfix session
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[root@mail ~]# telnet mail smtp

Replace mail with the name of your server. We should not use localhost since localhost is a trusted client ip

address. And make sure the domain name you specified does not resolve to 127.0.0.1 which is the IP address of

localhost.

Trying 192.168.0.1...Connected to mail.acme.local (192.168.0.1).

Escape character is '^]'.

220 mail.acme.local ESMTP Postfix

ehlo localhost

250-mail.acme.local

250-PIPELINING

250-SIZE 10240000

250-VRFY

250-ETRN

250-AUTH LOGIN PLAIN

250-AUTH=LOGIN PLAIN250-ENHANCEDSTATUSCODES

250-8BITMIME

250 DSN

Note the new250-AUTH lines. See the old SMTP Telnet Test.

mail from:

250 2.1.0 Ok

rcpt to:

554 5.7.1 : Relay access denied

It works, now to check if we can send it after authenticating.

auth plain AGpvaG5kb2UAcGFzc3dvcmQ=

235 2.0.0 Authentication successful

rcpt to:

250 2.1.5 Ok

quit

221 2.0.0 Bye


[root@mail ~]#

You can send to email addresses belonging to your domain without authentication. This is normal as it enables

you to receive mail from the outside.

The gibberish text afterAUTH PLAIN (http://www.linuxmail.info/postfix-smtp-auth-dovecot-sasl/ ) is

the base64 encoded value of the user namejohndoe and passwordpassword. You can generate your own base64 text

using the form below.

Top of Form
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User Name :

Password :

Result :

Bottom of Form


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