ANTI-SPAM CONFIGURATION
The anti-spam module of IEMS provides you with options to control the reception of unwanted messages. It also provides control on what sites can use IEMS as a mail relay. The anti-spam configuration is presented in a two-column table format. The left column contains the Spammer Address/Domain Restriction parameters, while the right column contains the IP Address Access Control parameters.
To configure the different anti-spam capabilities do the following:
- Tick the check box of the anti-spam capabilities you wish to enable namely:
- "Mail From" during SMTP connection
If enabled, the anti-spam module will scan for configured addresses/domains during the Mail From command in a SMTP connection and reject the message if a match is found.
- From
If enabled, the anti-spam module will scan for configured addresses/domains in the From header and reject the message if a match is found.
- Reply-ToIf enabled, the anti-spam module will scan for configured addresses/domains in the Reply-to header and reject the message if a match is found.
- Resent-FromIf enabled, the anti-spam module will scan for configured addresses/domains in the Resent-from header and reject the message if a match is found.
- SenderIf enabled, the anti-spam module will scan for configured addresses/domains in the Sender header and reject the message if a match is found.
- Return-pathIf enabled, the anti-spam module will scan for configured addresses/domains in the Return-path header and reject the message if a match is found.
- Reject with SMTP Error Code
The anti-spam module also allows the system administrator to specify whether to reject spam messages with Permanent or Temporary SMTP error code. If the Permanent SMTP error code is selected, the mail message will be rejected by SMTPD with a 533 error code and will be bounced back to the sender by the peer MTA. On the other hand, if the Temporary SMTP error code is selected, the message will be rejected by SMTPD with a 451 error code and will usually be queued up and re-tried by the peer MTA later.
- Reject Domain without MX/A RecordsIf enabled, SMTPD rejects the connection if there is no MX or A record defined in the DNS for the sender's domain.
- Enable RBL LookupWhen enabled, SMTPD will try to find and match the IP address of the connecting remote MTA against network databases of known spammers and reject the connection if a match is found. These databases consists of lists of IP addresses that are known to send spam mail or friendly to spammers and totally open for mail relaying.
- Enable Reverse DNS Lookup
When enabled, reverse DNS lookup is performed during SMTP session. During SMTP connection the remote MTA identifies itself to the local SMTPD server through the HELO/EHLO command w/c will then verifies if the domain name corresponds to the IP address of the remote MTA host by performing reverse DNS lookup.
- Reject Non-Resolvable IP
When enabled, SMTPD rejects the connection if the incoming IP address is non-resolvable which means that there is no DNS (PTR) record for this address.
Note: You need to enable the Enable Reverse DNS Lookup option to be able to use this feature.
- Reject Non-Match Host/Domain
When enabled, SMTPD matches the resolved domain name with the one declared by the remote SMTPC. If the two do not match, the connection is rejected. It is also used to compare the reverse address look-up values but does not continue to check for possible CNAME entries.
Note: You need to enable the Enable Reverse DNS Lookup option to be able to use this feature.
- Allow/Deny Incoming SMTP connection by DefaultIf the Allow Incoming SMTP Connection by Default option is selected, SMTPD accepts all IP address except for those listed in the Denied IP Addresses for Incoming SMTP Connection list under SMTP Connection Control. On the other hand, if the Deny Incoming SMTP Connection by Default option is selected, all IP address except for those listed in the Allowed IP Addresses for Incoming SMTP Connection list under SMTP Connection Control is rejected.
- Allow/Deny Mail Relaying by Default
If the Allow Mail Relaying by Default option is selected, SMTP allows mail relaying for all IP address except for those listed in the Denied IP Addresses for Mail Relay list under Mail Relay Control. On the other hand, if the Deny Mail Relaying by Default is selected, all IP address except for those listed in the Allowed IP Addresses for Mail Relay list under Mail Relay Control is prohibited for mail relaying.
- Click the Submit button to save the settings.