I have a dedicated server on 1&1 and I manage it with Plesk. The problem is that if I try to send a mail outside the server, I must to authenticate with the email and the password, but if I send an email to a address inside of my server I don't need neither email or password. This is a problem because the spammers are sending mails without any problem to the server accounts. We are receiving about 900 - 1200 emails everyday! What can I do?
I use qmail on CentOS