How to check if system has internet connection and can send email (via Shell)?

Question

I would like to know if server has access to internet and if it can send email with the help of a python script. Server OS is Red Hat Enterprise 5. When I open firefox and enter an url, it can't connect. What shell commands should I use to check availability of sending email?

Solution 1

First make sure that you are connected to the internet by trying a ping command to one of the most popular site.

Example: ping www.google.com

This will make sure you have the internet connectivity.

Solution 2

You can also try mailx on your system but this won't tell you anything about sending mail. You will need an SMTP host for that.

Try to telnet to a known mailhost on port 25:

telnet (name of mail host) 25

if you get a connection you should be in business, otherwise the request will block and make you wait.

Comments

[Admin]

You mean you think you're on a connection with HTTP firewalled but SMTP permitted?

[Admin]

Yes, exactly. How to tell?

[Admin]

See below. If you can communicate via telnet on port 25 you can connect via SMTP - if you can't, you can't.

[Omar Malas]

I get this error: Escape character is '^]'. 421 4.3.2 Service not available Connection closed by foreign host. What is wrong?

[lonstar]

Your question was " What shell commands should I use to check availability of sending email?" - the telnet command connected to the foreign host, but the host rejected the connection. This is common to prevent spamming. However, it does answer your questions 1) your server does have access to the internet, and 2) it is able to communicate on port 25.