Daniel, The original purpose of the setting was to prevent someone from attempting to DoS/crash the services by flooding them with data. Presently, the most common cause for problems related to this settings are network issues which result in corrupt data being received by SMTP/POP3/IMAP4. It is possible that a broken MUA/MTA is sending data strings out of sequence, but this should be very rare.
To explain the documentation further, most SMTP commands are just a few characters (MAIL FROM: <[EMAIL PROTECTED]>, RCPT TO: <[EMAIL PROTECTED]>). A typical message delivery sequence looks like (heavily abbreviated for the sake of my wrists): C> connect S> 220 mail.domain.com C> EHLO/HELO S> 250 OK C> MAIL FROM S> 250 OK C> RCPT TO S> OK C> DATA S> 354 C> message body C> end of message S> 250 OK C> QUIT S> 221 Only after the client has told the server that it is ready to start sending a message (by sending the DATA command) will IMail allow more than 512 characters in an SMTP command from the client. Once the client sends the EOM command, the restriction is back in place. Again, a broken mail client sending the message body out of sequence could trigger this, but it's most commonly from a broken network packet. Once we get the bogus packet, we immediately dump the network connection. If you have the setting disabled, then the client can connect again later. But, if you have the 'auto-deny' setting enabled, then we will not allow any further connections to the service from the IP that generated the problem until the service is restarted. Hope this helps. Have a good one, Christian -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Daniel Ivey Sent: Wednesday, November 03, 2004 11:56 AM To: '[EMAIL PROTECTED]' Subject: [IMail Forum] smtp security settings Is anyone running Imail Server version 8.13 with the "Auto-deny possible hack attempts" option enabled? If so, has it caused any problems on your server? What exactly does it do? I have read the Ipswitch manual and am still a little unclear as to what it means when it says "If more than 512 characters are sent during anything but the SMTP DATA command". Thanks in advance. Daniel ======================= Daniel Ivey GCR Company / GCR Online Voice: 434 - 570 - 1765 Fax: 434 - 572 - 1981 [EMAIL PROTECTED] To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
