You need to define the shell variables as follows:

HTTP_PROXY={YOUR-PROXY-Server-IP-HERE}:{YOUR-PROXY-SERVER-Port-Here}
FTP_PROXY={YOUR-PROXY-Server-IP-HERE}:{YOUR-PROXY-SERVER-Port-Here}

You can put above two directives in a file called ~/.wgetrc:

echo 'HTTP_PROXY=192.168.1.254:3128'>> ~/.wgetrc
echo 'FTP_PROXY=192.168.1.254:3128'>> ~/.wgetrc

Now you can use wget:
$ wget http://example.com/file.tar.gz
You can also define shell variables as follows:
export http_proxy=http://192.168.1.254:3128/
OR you can pass the proxy username and password as follows:
wget --proxy-user=YOUR-USERNAME-HERE --proxy-password=YOUR-PASSWORD-HERE http://nixcraft.com/file.tar.gz

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.

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;

1. /etc/sysconfig/network : Turn on networking in this file.
2. /etc/sysconfig/network-scripts/ifcfg-eth0 : Set default IPv6 router IP and server IP address in this file.

Open /etc/sysconfig/network file, enter:
# vi /etc/sysconfig/network
Append following line:

NETWORKING_IPV6=yes

Open /etc/sysconfig/network-scripts/ifcfg-eth0 (1st network config file)
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
Append following config directives for IPv6:

IPV6INIT=yes
IPV6ADDR=<IPv6-IP-Address>
IPV6_DEFAULTGW=<IPv6-IP-Gateway-Address>

Here is my sample file with mix of IPv4 and IPv6 assigned to eth0:

DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
HWADDR=00:30:48:33:bc:33
IPADDR=202.54.1.5
GATEWAY=202.54.1.3
NETMASK=255.255.255.248
IPV6INIT=yes
IPV6ADDR=2607:f0d0:1002:0011:0000:0000:0000:0002
IPV6_DEFAULTGW=2607:f0d0:1002:0011:0000:0000:0000:0001

Where,

• NETWORKING_IPV6=yes|no – Enable or disable global IPv6 initialization.
• IPV6INIT=yes – Enable or disable IPv6 configuration for all interfaces.
• IPV6ADDR=2607:f0d0:1002:0011:0000:0000:0000:0002 – Specify a primary static IPv6 address here.
• IPV6_DEFAULTGW=2607:f0d0:1002:0011:0000:0000:0000:0001 – Add a default route through specified gateway.

Save and close the file. Restart networking:
# service network restart
Verify your configuration by pinging ipv6 enabled site such as ipv6.google.com:
$ ping6 ipv6.google.com
Sample output:

PING ipv6.google.com(2001:4860:b002::68) 56 data bytes
64 bytes from 2001:4860:b002::68: icmp_seq=1 ttl=59 time=93.2 ms
64 bytes from 2001:4860:b002::68: icmp_seq=2 ttl=59 time=95.0 ms
64 bytes from 2001:4860:b002::68: icmp_seq=3 ttl=59 time=94.2 ms
64 bytes from 2001:4860:b002::68: icmp_seq=4 ttl=59 time=95.2 ms
64 bytes from 2001:4860:b002::68: icmp_seq=5 ttl=59 time=94.8 ms
64 bytes from 2001:4860:b002::68: icmp_seq=6 ttl=59 time=95.1 ms
64 bytes from 2001:4860:b002::68: icmp_seq=7 ttl=59 time=93.3 ms
64 bytes from 2001:4860:b002::68: icmp_seq=8 ttl=59 time=93.8 ms

— ipv6.google.com ping statistics —
8 packets transmitted, 8 received, 0% packet loss, time 7010ms
rtt min/avg/max/mdev = 93.268/94.376/95.268/0.799 ms

Traces path to a network host, enter:
$ traceroute6 ipv6.google.com
Print default IPv6 routing table, enter:
$ route -n -A inet6
Sample output:

Kernel IPv6 routing table
Destination Next Hop Flags Metric Ref Use Iface
::1/128 :: U 0 42531 1 lo
::62.41.14.144/128 :: U 0 0 1 lo
::127.0.0.1/128 :: U 0 0 1 lo
::/96 :: U 256 0 0 sit0
2001:470:1f04:55a::2/128 :: U 0 15201 1 lo
2001:470:1f04:55a::/64 :: U 256 0 0 sit1
fe80::4833:22f4/128 :: U 0 0 1 lo
fe80::212:3fff:fe75:fa0d/128 :: U 0 0 1 lo
fe80::/64 :: U 256 0 0 eth0
fe80::/64 :: U 256 0 0 sit1
ff00::/8 :: U 256 0 0 eth0
ff00::/8 :: U 256 0 0 sit1
::/0 :: U 1 0 0 sit1

1. /etc/modprobe.conf – Kernel driver configuration file.
2. /etc/sysconfig/network – RHEL / CentOS networking configuration file.

/etc/modprobe.conf

Edit /etc/modprobe.conf, enter:
# vi /etc/modprobe.conf
Append the following line:

install ipv6 /bin/true

Save and close the file.

/etc/sysconfig/network

Edit /etc/sysconfig/network, enter:
# vi /etc/sysconfig/network
Update / add as follows:

 
NETWORKING_IPV6=no
IPV6INIT=no

Save and close the file. Restart networking service
# service network restart
# rmmod ipv6
Alternatively, simple reboot the box:
# reboot
Verify IPv6 is disabled, enter:
# lsmod | grep ipv6
# /sbin/ifconfig