Restrict outgoing SMTP, why is bad to allow?

[benito]

Hello!

I have this settings OFF in all my shared hosting servers because many customers needs to use external SMTP for their needs. I think if its enabled by default is because outgoing SMTP is bad but I can't understand why.

My question is, just that, why is good to turn ON "Restrict outgoing SMTP" option?

Thanks!

 

[cPRex]

Hey hey! Our documentation on that feature shows this:

"This interface allows you to configure your server so that only the mail transport agent (MTA), Mailman mailing list software, and the root user can connect to remote SMTP servers. This will deny other users and services the ability to bypass your mail server to directly send mail, which is common practice for spammers."

With this enabled, you have to be the root user or Exim in order to send a message. Without this enabled, it's possible that spam scripts could be run and send as many messages as they want on the system.

 

[quietFinn]

If outgoing SMTP is not restricted any user can send spam and you most likely don't know it before your server's IP is blacklisted.
When all outgoing emails go throug Exim it's quite easy to notice and track spammers.