SMTP servers

If you have just installed SMTP server I suggest immediately lock it down so no other users (remote) can use it to relay email. There are many ways to test out for a open relay - you can use online service to check it remotely or if you have a remote shell, you can use telnet.

Open relaying has been a big problem for folks who do not know much about mail service and usually their smtp IP gets blocked due to spam - relayed email.