Usually, you do not need to setup an email server under Linux desktop operating system. Most GUI email clients (such as Thunderbird) supports Gmail POP3 and IMAP configurations. But, how do you send mail via the standard or /usr/bin/mail user agents or a shell script? Programs such as sendmail / postfix / exim can be configured as a gmail smarthost but they are largely overkill for this use.

You can use gmail as a smart host to send all messages from your Linux / UNIX desktop systems. You need to use a simple program called ssmtp. It accepts a mail stream on standard input with recipients specified on the command line and synchronously forwards the message to the mail transfer agent of a mailhub for the mailhub MTA to process. Failed messages are placed in dead.letter in the sender’s home directory.

Install ssmtp

Type the following command under CentOS / RHEL / Red Hat / Fedora Linux:
# yum install ssmtp
Type the following command under Debian / Ubuntu Linux:
# apt-get update && apt-get install ssmtp

Configure gmail as a smarthost

Open /etc/ssmtp/ssmtp.conf, enter:
# vi /etc/ssmtp/ssmtp.conf
Update file with the following settings:

AuthUser=vivek@gmail.com
AuthPass=Your-Gmail-Password
FromLineOverride=YES
mailhub=smtp.gmail.com:587
UseSTARTTLS=YES

Also, make sure you disable Sendmail:
# service sendmail stop
# chkconfig sendmail off
# mkdir /root/.bakup
# mv /usr/sbin/sendmail /root/.bakup
# ln -s /usr/sbin/ssmtp /usr/sbin/sendmail
Now, you can use mail / mailx command to send email messages. You can also write a shell script to backup your files and email to somewhere else (see below). You can test settings using following syntax:
$ echo "This is a test" | mail -s "Test" vivek@nixcraft.co.in

A note about sSMTP

sSMTP works well for desktop systems, but it is not a replacement for Sendmail / Postfix / Exim / Qmail for email server environment. This software is perfect for a single user system.

We talked about some of the benefits of setting up an email server in Linux and how you can use python to send email. Now we are going to look at how you can send email from Perl.
The Code

use Net::SMTP::TLS;
my $mailer = new Net::SMTP::TLS(
‘smtp.gmail.com’,
Hello => ‘smtp.gmail.com’,
Port => 587,
User => ‘username’,
Password=> ‘password’);
$mailer->mail(‘from@domain.com’);
$mailer->to(‘to@domain.com’);
$mailer->data;
$mailer->datasend(“Sent from perl!”);
$mailer->dataend;
$mailer->quit;

Edit /etc/dovecot.conf, find:

mechanisms = plain

Add after:

passdb passwd-file {
args = /etc/dovecot-deny.%Ls
deny = yes
}

Now use the following script to disable IMAP (or POP3 (replace IMAP with POP3 in the script)) access (usage: ./script allow/deny usename):

#!/bin/sh
#
# Script used to deny IMAP access for a particular user

show_help()
{
echo “IMAP allow/deny script.”;
echo “”;
echo “Usage: $0 allow/deny username”;
echo “”;
}

if [ $# -eq 2 ]; then
echo “Using $2.”
else
show_help;
exit 1;
fi

IMAPDENY=/etc/dovecot-deny.imap

OS=`uname`;

if [ $1 = "allow" ]; then
OPTION=allow
else
OPTION=deny
fi

USER=$2

if [ ${OPTION} = "allow" ]; then
if [ "`grep -c \"${USER}\" ${IMAPDENY}`" = "0" ]; then
echo “User ${USER} is already allowed.”;
exit 1;
fi
fi

if [ ${OPTION} = "deny" ]; then
if [ "`grep -c \"${USER}\" ${IMAPDENY}`" = "1" ]; then
echo “User ${USER} is already denied.”;
exit 1;
fi
fi

if [ ! -d /home/${USER} ]; then
echo “User ${USER} does not exist.”
exit 1;
fi

if [ ${OPTION} = "allow" ]; then
perl -pi -e “s/${USER}\n//g” ${IMAPDENY}
fi

if [ ${OPTION} = "deny" ]; then
echo “$USER” >> ${IMAPDENY}
fi
exit 0;

I’ve just installed this plugin, I have wp-smtp-mail plugin installed as well. The test thing on the plugin works, however I receive an error when trying to utilize the actual contact form.

The error it self is:

The e-mail could not be sent.
Possible reason: your host may have disabled the mail() function.

http://wordpress.org/extend/plugins/si-contact-form/

solution:

Some web hosts restrict sending mail unless the “From” address is a
valid address on the same domain.
Try step 3 of the “email not working” in the FAQ

http://wordpress.org/extend/plugins/si-contact-form/faq/

The script found on the following site http://bashcurescancer.com

The a script is called monitorCpuUsage.sh. It is meant to be called from crontab and to inform you of processes or users who maybe using excessive amounts of cpu.

Here is the help screen:

# ./monitorCpuUsage.sh -h
Usage: monitorCpuUsage.sh
-u starting uid, must be an integer greater than or equal to 0 (only used with “-w users”)
-m max cpu, must be an integer greater than or equal to 0 and less than 100
-w what to watch, must be “users” or “procs”
-e must contain an email address
-d specifies debug mode in which -e, -m, and -u do not need to be specified.

Here the script in use. I used the -d option which means the script sets the “maximum cpu allowed to -1″ and prints to the screen rather than emailing.

# ./monitorCpuUsage.sh -w users -d -u 100
Mon Oct 15 03:15:54 EDT 2007
User brock is using 0% cpu.
User nfsnobody is using 0% cpu.
User USER is using 0% cpu.

Watching processes…again with -d specified.

# ./monitorCpuUsage.sh -w procs -d
Mon Oct 15 03:17:20 EDT 2007
Process aio/0 is using 0% cpu.
Process atd is using 0% cpu.
Process bash is using 0% cpu.
Process crond is using 0% cpu.
Process dhclient is using 0% cpu.
Process events/0 is using 0% cpu.
Process httpd is using 0% cpu.
Process init is using 0% cpu.
Process java is using 0% cpu.
Process jfsCommit is using 0% cpu.
Process jfsIO is using 0% cpu.
Process jfsSync is using 0% cpu.
Process kblockd/0 is using 0% cpu.
Process kcryptd/0 is using 0% cpu.
Process khelper is using 0% cpu.
Process kjournald is using 0% cpu.
Process klogd is using 0% cpu.
Process ksnapd is using 0% cpu.
Process ksoftirqd/0 is using 0% cpu.
Process kswapd0 is using 0% cpu.
Process kthreadd is using 0% cpu.
Process lockd is using 0% cpu.
Process mingetty is using 0% cpu.
Process monitorCpuUsage is using 0% cpu.
Process mysqld is using 0% cpu.
Process mysqld_safe is using 0% cpu.
Process nfsd is using 0% cpu.
Process pdflush is using 0% cpu.
Process portmap is using 0% cpu.
Process ps is using 0% cpu.
Process rpc.mountd is using 0% cpu.
Process rpc.rquotad is using 0% cpu.
Process rpc.statd is using 0% cpu.
Process rpciod/0 is using 0% cpu.
Process sendmail is using 0% cpu.
Process sshd is using 0% cpu.
Process su is using 0% cpu.
Process syslogd is using 0% cpu.
Process xfs is using 0% cpu.
Process xfsdatad/0 is using 0% cpu.
Process xfslogd/0 is using 0% cpu.