Sets the maximum number of simultaneous outbound connections. The default is 2,000 connections.
Maximum number of connections from a single IPv4 address or IPv6 range
Sets the maximum number of simultaneous outbound connections that can be made from a single IPv4 address or IPv6 range.
The default value is 20 connections.
IPv6 CIDR prefix for maximum number of connections from a single IPv6 range
Describes the CIDR prefix to be used if an IPv6 range is used.
The prefix value must be an integer from 0 to 128. The default value is 128.
Maximum number of connections from a single IP address
Sets the maximum number of simultaneous outbound connections that can be made from a single IP address. The default is 20 connections.
Maximum message size in bytes
Sets the maximum size allowable for a message before it is rejected. The default is 10,485,760 bytes.
Maximum number of recipients per message
Indicates the maximum number of recipients permitted to receive a message. The default is 1,024 recipients.
Maximum number of messages per session
Indicates the maximum number of email messages that are permitted in a single session.
The default value is 0 if you have upgraded from a prior version. The default value is 100 if this is an initial installation.
Default domain for sender addresses with no domain
Sets a default domain when none can be found in the message.
Maximum number of messages in outbound queue
Sets the maximum threshold. When this threshold is met or exceeded, alerts are sent (when enabled) and connections are deferred. The default is 5,000 messages.
Maximum number of outbound recipients per sender in a specific time-frame
Sets the maximum number of recipients to which a sender can send mail in the specified time-frame (per minute or per hour).
The default value is 0. The value 0 indicates that unlimited email messages are permitted in a single session.
Defer new connections when outbound queue is full
When the number of messages in the outbound queue reaches or exceeds the maximum, defers messages, by issuing an SMTP 4xx error. If unchecked, messages are accepted for as long as resources allow.
Insert RECEIVED header
Places a RECEIVED header in the message during outbound SMTP processing when checked. When unchecked, no RECEIVED header is inserted during outbound SMTP processing. If this option and Strip pre-existing RECEIVED headers are both checked, the outbound SMTP RECEIVED header remains when the message goes to the delivery queue.
Strip pre-existing RECEIVED headers
Removes all RECEIVED headers for outbound messages when checked. When headers are stripped, message looping can occur depending on the settings of other MTAs. When unchecked, RECEIVED headers remain in the message during outbound processing. The RECEIVED header for outbound SMTP processing remains in the message when both Insert RECEIVED header and Strip pre-existing RECEIVED headers are checked.
Enabling this setting can reduce your ability to diagnose message flow issues.
Enable reverse DNS lookup
Causes the system to perform reverse DNS lookup on the SMTP client IP addresses to resolve the IP address to a name when checked. This is the default condition. When unchecked, reverse DNS lookup is not performed for outbound messages.
When you enable the global rDNS settings on Protocols > SMTP > Settings page, you override this local setting.
This setting controls how long the MTA waits for a request or response from the connecting MTA. If this limit is exceeded, the appliance will drop the connection.