I notice that i have ~105.000 e-mails send / week and ~10200 e-mails in queque. Also the outlook express can`t send e-mail (messages remain in outbox even when i press send/receive button) if it sends I get the following error: Remote host said: 550 Denied by policy: Sender is listed on DNS-based RBL. After a reboot of server it works for about 30 min. I have found the computer that send all this spam and disconnect it from network but the smtp server still freeze after a few min.
I have enabled SPAM filter and Antivirus filter and SMTP proxy. Problem is that virus keep send spam e-mails somehow.
My question is how can i force SME to send e-mails only from SMTP server and SMTP server to accept only connection from internal network and require authentication before sending ?