Using the SMTP Screen you can block IP addresses that connect to MDaemon too many times within a specified number of minutes. You can also block those the cause too many failed RCPTs, and those that send too many RSET commands. The SMTP Screen requires Dynamic Screening and uses the Dynamic Blacklist and Dynamic Whitelist.

Block IPs that connect more than [X] times in [X] minutes

Click this check box if you wish to temporarily block IP addresses that connect to your server an excessive number of times in a limited time period. Specify the number of minutes and the number of connections allowed in that period. The addresses are blocked for the amount of time specified on the Auth Failure Tracking screen. This option also applies to POP and IMAP connections.

Block IPs that cause this many failed RCPTs

When an IP address causes this number of "Recipient unknown" errors during a mail session it will be automatically blocked for the amount of time specified on the Auth Failure Tracking screen. Frequent "Recipient unknown" errors are often a clue that the sender is a spammer, since spammers commonly attempt to send messages to outdated or incorrect addresses.

Block IPs that send this many RSETs (0 = no limit)

Use this option if you wish to block any IP address that issues the designated number of RSET commands during a single mail session. Use "0" if you do not wish to set a limit. There is a similar option on the Servers screen under Server Settings that can be used to set a hard limit on the allowed number of RSET commands. A blocked IP address will be blocked for the amount of time specified on the Auth Failure Tracking screen.

Close SMTP session after blocking IP

Enabling this option causes MDaemon to close the SMTP session after the IP address is blocked. This is enabled by default.

Do not block IP when when SMTP authentication is used

Click this checkbox if you want senders who authenticate their mail sessions before sending to be exempt from Dynamic Screening. This is enabled by default.

White list

Click this button to open the Dynamic Whitelist. IP addresses listed there are exempt from SMTP Screening.

Advanced

This button opens the Dynamic Screening dialog.