Configuring advanced MTA settings

To modify the advanced settings of MTA:

1. In the application web interface window, select the Settings → Built-in MTA → Advanced Settings section.
2. In the SMTP greeting text field, type the text that will accompany code 220 in the SMTP greeting (smtpd_banner).

   Default value: $myhostname ESMTP MTA.

3. In the Maximum connection attempts field, specify the maximum number of connection attempts by one remote SMTP client to the service of the SMTP server per minute (smtpd_client_connection_rate_limit).

   Specify 0 if no limit is required.

   Default value: 0 (no limit).

4. In the Maximum simultaneous connection attempts field, specify the maximum number of simultaneous connection attempts by one remote SMTP client to the SMTP server (smtpd_client_connection_count_limit).

   Specify 0 if no limit is required.

   Default value: 50.

5. In the Maximum mail delivery requests field, specify the maximum number of message delivery requests from one remote SMTP client to the SMTP server per minute (smtpd_client_message_rate_limit), regardless of whether this mail server accepts these messages or not.

   Specify 0 if no limit is required.

   Default value: 0 (no limit).

6. In the Maximum SMTP session length field, specify the maximum period of time during which a request has to be received from the remote SMTP client and a response sent by the SMTP server (smtpd_timeout). In the drop-down list next to the field, select units of measurement.

   The default value is 30 seconds.

7. In the Maximum queue lifetime for a message field, specify the time period for storing messages in the queue with a transient error status (maximal_queue_lifetime), after which time the messages are considered undeliverable. In the drop-down list next to the field, select units of measurement.

   Default value: 3 days.

8. In the Maximum queue lifetime for a bounce message field, specify the time period for storing bounce messages in the queue with a transient error status (bounce_queue_lifetime), after which time the messages are considered undeliverable. In the drop-down list next to the field, select units of measurement.

   Default value: 3 days.

9. In the BCC address for all messages field, specify an optional email address for a BCC ("blind carbon copy") recipient of all messages received by the MTA mail transfer agent (always_bcc).
10. Use the Check addresses format for RFC 821 compliance toggle switch to enable or disable the checking of email addresses in SMTP MAIL FROM and RCPT TO to verify that such addresses are in angle brackets and do not contain RFC 822 comments and phrases (strict_rfc821_envelopes).

    This scanning prevents receipt of messages from poor-quality software.

    By default, this authentication is enabled.

11. Use the Disable recipient verification SMTP VRFY toggle switch to enable or disable SMTP VRFY command (disable_vrfy_command).

    The SMTP VRFY command prevents specific services from collecting email addresses.

    By default, this authentication is disabled.

12. In the EHLO keywords not sent by SMTP server in response settings group, select check boxes next to those case insensitive EHLO commands, which your SMTP server will not announce in response to an EHLO request from an external SMTP client (smtpd_discard_ehlo_keywords).

    Default values: dsn, etrn.

13. If you want Kaspersky Secure Mail Gateway to reject a message delivery request if the domain from the RCPT TO header does not contain MX and A records of the DNS server, or the MX record is distorted (for example, a zero-length MX host address is specified), set the Reject messages for unknown recipient domains toggle switch to Enabled.

    By default, request rejection is enabled.

14. In the Reject messages for recipients drop-down list, select one of the following modes of SMTP Recipient Address Verification:

    SMTP verification of email addresses involves verifying the existence of recipient email addresses.

    • Do not reject.

      Recipient verification is not performed.

    • Reject for unverified recipients.

      The application rejects the message if the recipient's server is unavailable or rejects the request (reject_unverified_recipient).

    Default value: Reject for unverified recipients.

    SMTP Recipient Address Verification is not performed when Kaspersky Secure Mail Gateway receives messages from trusted network hosts.

    If SMTP verification of recipient addresses is disabled, a delivery failure notification is sent when an attempt is made to deliver a message to a nonexistent address. This increases the volume of email traffic and may increase the load on the mail server.

15. Click Save.

Advanced MTA settings are configured.