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 Block List and Dynamic Allow List.
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unknown" errors are often a clue that the sender is a spammer, since spammers commonly attempt to send messages to outdated or incorrect addresses.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.
Send notification when IP is blocked
By default, when an IP addresses is automatically blocked by the Dynamic Screening system, the Dynamic Screening IP Address Blocking Reports options will be used to notify you of that action. Clear this checkbox if you do not wish to be notified when an IP address is blocked due to SMTP Screening feature.
Allow list
Click this button to open the Dynamic Allow List. IP addresses listed there are exempt from SMTP Screening.
Advanced
This button opens the Dynamic Screening dialog.
IP History
Save IP addresses of login attempts so new and previously-failed IPs can be reported in the Screening log
By default, SMTP/IMAP/POP login attempts are saved, so that new and previously-failed IPs can be reported in the Screening log.
Forget IP addresses after this many days [xxx] (0 = never)
Use this option to specify how long before the saved IP addresses will be pruned. They are saved 365 days by default. Use "0" in this option if you never wish to delete them.
