This topic explains how to configure the behavior of the SMTP service when it is receiving email messages from other SMTP servers.
Procedure
1. Click SMTP > Configuration in the navigation pane.
2. Click the Receiving SMTP > Settings tab.
3. Provide the following information:
Option Description
Enable Logging Instructs the SMTP service to write information about email message deliveries to a log file. This log file is named smtp-yyyymmdd0000.
Note: The SMTP service logs several lines to its log file for each delivery attempt. For successful delivery attempts, the SMTP service writes one log entry for each recipient of an email message and, additionally, one log entry if the transmission of the email message was successful.
Port Specifies the port number on which the SMTP service is
listening.
Default: port 25
Attention: If you change this value, other SMTP servers might not be able to transmit email messages to Lotus Protector for Mail Security, because those servers are trying to open a connection to the default SMTP port (which is TCP port 25).
If you must change the listening port of the SMTP service, consider adding a translation rule at the firewall.
Max Recipients per Message SMTP server might try to transmit an email message to multiple recipients within a single transaction.
This value regulates the maximum number of recipients allowed in a single message transaction.
Default: 100 recipients
Max Messages per Session An SMTP server might try to deliver several email messages to Lotus Protector for Mail Security using the same connection.
This value defines how many email messages an SMTP server is allowed to transmit, before it is forced to establish a new connection to Lotus Protector for Mail Security.
Session Timeout Specifies the amount of time before an SMTP session times out.
A timeout can occur when the SMTP service does not receive any data from the SMTP server within the configured amount of time. In this case, the SMTP service closes the connection to the peer.
Default: 60 seconds
Option Description
Max Message Size (KB) Defines the maximum size of an email message, in Kilobytes, that the SMTP service will accept from other SMTP servers.
Note: If you set this value to zero, the SMTP service will allow any message size.
Allow NULL Sender If enabled, the SMTP service accepts email messages even if the SMTP server did not specify an originator with the MAIL FROM: command.
If disabled, the SMTP service rejects the transmission.
Max SMTP Errors per Session Defines how many protocol errors, such as syntax errors, an SMTP server is allowed to cause before the SMTP service enforces the termination of the connection.
Check Mailer Domain Select if you want the SMTP service to perform a DNS lookup on an MX record for the domain of the sender's email address, as provided by the MAIL FROM command, for validation.
The SMTP service will only accept email messages from senders whose email address domain part has a valid MX record.
Max MTA Hops Defines the maximum number of SMTP servers an email
message is allowed to be relayed by so far, determined by the number of Received Fields in the Header of the message.
If this number exceeds the defined limit, the SMTP service rejects the transmission.
Default: 20
Enable Reverse DNS Lookup Select if you want the SMTP service to determine if the IP address of an SMTP server resolves to an actual valid host name (meaning a DNS record exists that is pointing to the IP address of the peer).
If the SMTP service cannot resolve the host name of the SMTP server, it will not accept any email messages from this SMTP server.
Return Path Domain Check Select if you want the SMTP service to verify that the domain part of the sender's email address, provided by the MAIL FROM command, is compliant with RFC2821 Section 4.1.2.
This means that the domain part only contains letters, numbers, hyphens, and dots in a specific format.
Helo Domain Check Select if you want the SMTP service to verify that the argument, provided by the HELO/EHLO command, is compliant with RFC2821 Section 4.1.2.
This means that the domain part only contains letters, numbers, hyphens, and dots in a specific format or an IP address enclosed in square brackets.
Option Description
Forward Path Domain Check Select if you want the SMTP service to verify that the domain part of the recipient's email address, provided by the RCPT TO command, is compliant with RFC2821 Section 4.1.2.
This means that the domain part only contains letters, numbers, hyphens, and dots in a specific format.
SMTP Greeting Specifies the welcome message (greeting) the SMTP
service sends to an SMTP client when a connection is established, meaning that it is ready to process commands.
Received Header The SMTP service adds information to the email message header (Received Field) such as when and by whom the email message was transmitted. You can regulate the amount of information in this header field using one of the following levels:
v Standard (client IP shown, server IP not): The SMTP service adds the IP address of the SMTP server to the header field, but omits its own IP address.
v Verbose (client IP shown, server IP shown): The SMTP service adds the IP address of the SMTP server, as well as its own IP address to the header field.
v Strict (no IP shown): The SMTP service does not add any IP addresses at all (not its own or the IP address of the sender) to the header field.
Important: If you set the Received Header Type to Strict (no IP shown), and then open ports on your corporate firewall to receive SMTP traffic, the analysis modules in the Sender Policy Framework will not work because these modules rely on information in the received header.