Configure your SMTP Server in Linux/Unix

Unable to connect SMTP port,There is a easy to check this.
(ptian) ptian- telnet server_host 25
Trying ip...
telnet: Unable to connect to remote host: Connection refused
This means probably, SMTP port 25 is not open.

Solution:
To resolve the issue,you need login with root user.

1.Verify sendmail packages
In order to configure sendmail, you will require the sendmail and sendmail-cf packages.

[root@bej301441 oracle]$ rpm -qa | grep sendmail
sendmail-doc-8.13.8-8.1.el5_7
sendmail-8.13.8-8.1.el5_7
sendmail-devel-8.13.8-8.1.el5_7
sendmail-devel-8.13.8-8.1.el5_7
sendmail-cf-8.13.8-8.1.el5_7
[root@bej301441 oracle]$

2.changes to /etc/mail/sendmail.mc

2.1 Uncomment the definition SMART_HOST
define(`SMART_HOST', `your-smtp-server')Note: replace `your-smtp-server' with whatever you use internally: `servername.domain.com'
2.2 Comment below line

From: DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')
To:   dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')

3.Start/Restart sendmail

root@bej301441 admin]# /sbin/service sendmail status
sendmail (pid  2373) is running...
[root@bej301441 admin]# /sbin/service sendmail stop
Shutting down sm-client:                                   [  OK  ]
Shutting down sendmail:                                    [  OK  ]
[root@bej301441 admin]#
[root@bej301441 admin]# /sbin/service sendmail start
Starting sendmail:                                         [  OK  ]
Starting sm-client:                                        [  OK  ]
[root@bej301441 admin]#

4. Test outbound mail

mutt -s "test email" test@abc.com < /dev/null

Also,test telnet

(ptian) ptian- telnet xxx.com 25
Trying xxxxxxxxIP...
Connected to xxx.com (xxxxxxIP).
Escape character is '^]'.

References
Workflow Notification Mailer Remains in Starting Status (Doc ID 1400353.1)
Enable outbound Sendmail on Linux (Doc ID 1353507.1)
How to Perform a Meaningful SMTP Telnet Test to Troubleshoot Java Mailer For Sending Email Notifications (Doc ID 753845.1) http://cybergav.in/2010/09/14/how-to-configure-sendmail-on-linux-to-use-smtp-mail-relays/