Mail command in linux

I'm trying to find out what emailing program (if any) is sending emails on my server. My employer has a few servers, most of which use , but on 2 of our servers I'm not finding an email program, but somehow email has been sent with it?

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I don't want to just install if something is already setup, I'm just unsure as to how to find out what is setup. The server is Ubuntu Server 12.04 LTS, and I'm using the PHP command.

The only information I can find to try answering my question is Sinan's question: How to find out what program is sending emails.

I tried both the answers there and found nothing.

does nothing, and is completely empty.

I tried using to see what happened when this file was executed, but I kept getting "permission denied", just like the below:

The file was very basic, just having the code:

It's possible I'm not using correctly, as this is my first time trying to use it.

I tried it on a server that I know sendmail is installed on and got the same message. I also tried running as the root user,

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how to check mail in linux