MailEnable Professional Guide
SMTP - IP Blocking
Services and Connectors > SMTP Connector > SMTP - IP Blocking

IP Blocking acts on the IP addresses that are reported as spam by web mail users. There are two types of blocking which is used by the SMTP service. There is a system level block and a post office level block. A system level block is an IP address which is blocked for the whole server and a post office level block is done for a connection which can be attributed to a post office.

When a message is blocked by the web mail, it will add the IP entry to the post office level spam directory. For each IP address added a separate file is created which has the time the message was reported as spam, the user that reported it and the message filename. The IP is also checked against whether it has been reported at the system level for that post office. If not, then a new file is created for this IP address. The system level file contains the timestamp of the report, and the post office that reported it.

Whitelisting an IP address will prevent it from being testing against the IP blocking list. Whitelisting can be done either by adding its IP address in the SMTP Whitelist, or by it being listed as an outbound whitelisted IP address. Local server IP addresses also cannot be blocked.

Connections are given an error when they perform a RCPT TO: SMTP command. When an IP address is blocked for the system level or post office level, the following message is in the SMTP Debug log:

ME-E011X: [socket number] Message blocked: (IP address) was found in reported in System Spam database.

ME-E011X: [socket number] Message blocked: (IP address) was found in reported in Postoffice Spam database.

The connecting server will be given the error:

452 The IP Address you are sending from was reported as a source of Spam. Please contact your e-mail administrator.

Refuse e-mail from IP addresses reported as sending spam

When enabled, the SMTP service will not accept emails coming from a blocked IP address. The service determines that an IP address is blocked by using the number of reports and a time frame, set by the “Reports required” and the “Expire after” text boxes.  System level records are checked first, then the post office level records. So in order for an IP address to be blocked for the whole server, it needs to be reported by more post offices than the “reports required” setting, and to be blocked to a post office needs to be reported just that many times by any post office user(s). This setting is only useful if either a post office or the server is set to allow users to mark sender IPs as a spam source, which is done either through the global web mail settings or the web mail settings for a post office.

Blocked Address Management

Since there can be a large number of blocked addresses reported, mailenable allows the management of such addresses. To remove an IP address that is blocked, select the “Remove IP…” button. To view details about a blocked IP address, select the “View Report…” button. When viewing a report about a spam item, the dialog displayed will indicate whether the IP address is a system level block or a post office level block.