SMTP advanced inbound settings

SMTP Advanced Settings—Inbound Configuration describes inbound SMTP settings that you can configure to further define the Scanner SMTP connections.
SMTP Advanced Settings—Inbound Configuration
Item
Description
Maximum number of connections
Sets the maximum number of simultaneous inbound 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 inbound connections that can be made from a single IPv4 address or IPv6 range. If Connection Classification is enabled, the settings for each Connection Class override this setting for IPv4 senders.
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 64.
Maximum number of connections from a single IP address
Sets the maximum number of simultaneous inbound connections that can be made from a single IP address. The default is 20. If Connection Classification is enabled, the settings for each Connection Class override this setting.
Maximum number of recipients per message
Sets the maximum number of recipients for 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.
This field is disabled if Connection Classification is enabled, and the settings for each Connection Class overrides the setting.
Maximum message size in bytes
Sets the maximum size of a message before it is rejected. The default is 10,485,760 bytes.
Maximum number of messages in inbound 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.
Defer new connections when inbound queue is full
When the number of messages in the inbound queue exceeds the maximum, defers messages, by issuing an SMTP 4xx error. If unchecked, messages are accepted for as long as resources allow.
Insert a RECEIVED header to inbound messages
Places a RECEIVED header in the message during inbound SMTP processing.
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 inbound messages.
When you enable the global reverse DNS settings on
Protocols > SMTP > Settings > SMTP
tab, under
DNS Validation
, you override this local setting.
Session Timeout
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.