Enable Outgoing Emails

	WARNING
	This is recommended only for advanced users, proceed with caution.

Here's how to enable outgoing emails on your Amahi server

NOTE: Make sure to use copy-paste to execute those commands. In particular, they contain back-ticks as the starting string delimiter, which can be hard to find on a keyboard!

As root user:

Option 1 (untested on Fedora 19)

SMTP_SERVER=your_isp_smtp_server
yum -y install sendmail-cf m4
cd /etc/mail
sed -ie "s/.*SMART_HOST.*/define(\`SMART_HOST', \`$SMTP_SERVER')dnl/" sendmail.mc
make
chkconfig sendmail on
service sendmail restart

Make sure to replace your_isp_smtp_server on the first line with the hostname or IP address of your ISP SMTP server.

If you need to connect to the SMTP server using port 587 (TLS/STARTTLS), you'll need to do this too:

cd /etc/mail
sed -ie "s/\(.*SMART_HOST.*\)/\1\ndefine(\`RELAY_MAILER_ARGS', \`TCP \$h 587')dnl\ndefine(\`ESMTP_MAILER_ARGS', \`TCP \$h 587')dnl/" sendmail.mc
make
service sendmail restart

If you want to use another port than 587, change that number in the above command (it's there twice), before executing it. If you already executed it, edit the sendmail.mc file, and search for 587 - it should appear there twice - change both.

If you need to provide a username and password to use the SMTP server, you'll need to do this too:

SMTP_SERVER=your_isp_smtp_server
USERNAME=your_smtp_username
PASSWORD=your_smtp_password
cd /etc/mail
chmod 600 access
echo "AuthInfo:$SMTP_SERVER \"U:$USERNAME\" \"P:$PASSWORD\" \"M:PLAIN\"" >> access
makemap -r hash access.db < access
sed -ie "s/.*confAUTH_MECHANISMS.*/define(\`confAUTH_MECHANISMS', \`EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl\nFEATURE(\`authinfo',\`hash \/etc\/mail\/access')dnl/" sendmail.mc
make
service sendmail restart
<pre>

== Option 2 (tested on Fedora 19)==
<pre>
su -
yum -y install sendmail-cf mailx
cp /etc/mail/sendmail.mc /etc/mail/sendmail.mc.orig
vi /etc/mail/sendmail.mc

Near the very bottom before MAILER insert the following lines. Sendmail is picky about the quotation marks: when I first pasted them, they were wrong and gave me a syntax error. This section is a combination of the two sources above which fixes the error in /var/log/maillog “no route to host” which apparently has nothing to do with DNS resolution.

define(`SMART_HOST',`smtp.gmail.com')dnl
define(`RELAY_MAILER_ARGS', `TCP $h 587')dnl
define(`ESMTP_MAILER_ARGS', `TCP $h 587')dnl
define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
FEATURE(`authinfo',`hash /etc/mail/auth/client-info')dnl
TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')

Then save. Back in the terminal:

mkdir /etc/mail/auth
vi /etc/mail/auth/client-info
AuthInfo:smtp.gmail.com "U:root" "I:<YOUR GMAIL USERNAME HERE>@gmail.com" "P:<YOU GMAIL PASSWORD HERE>"

Of course, fill out your real login info, save, and exit. The next section skips the part about the openssl certificates: I ran it, but it didn’t seen to be necessary on Fedora.

cd /etc/mail/auth
makemap hash client-info.db < client-info
chmod 700 /etc/mail/auth
chmod 600 /etc/mail/auth/*
cd /etc/mail
make
service sendmail restart

Finally, send a test email.

echo 'this is a test'| mail -s test_email user@example.com
If it fails, read /var/log/maillog and /var/log/messages.

Ref:  Sendmail SMTP Gmail Relay on Fedora-Centos-Redhat