Configuring Advanced SMTP Options

Use the options on the Advanced tab to fine-tune the mail queue, queue monitoring, and SMTP server settings.

Note
The default settings on this page are optimal for most organizations. It is not recommended that you make adjustments unless you have advanced knowledge of mail transfer agents and SMTP.

To configure advanced SMTP options:

If necessary, adjust the value of any of the following settings.

Mail queue settings

  • Queue run delay: The time between deferred queue scans by the queue manager. The deferred queue contains mail deliveries that have failed for a reason that may be temporary. This value should be less than or equal to the next two settings ("Min backoff time" and "Max backoff time"). The default is 180 seconds.
  • Minimum backoff time: The minimum amount of time between attempts to deliver a deferred message. The default is 180 seconds.
  • Maximum backoff time: The maximum amount of time between attempts to deliver a deferred message. The default is 4000 seconds.
  • Maximum queue lifetime: The maximum amount of time that a message is queued before it is returned as undeliverable. The default is 5 days.
  • Bounce queue lifetime: The maximum amount of time that a bounce message is queued before it is treated as undeliverable. The default is 5 days, which matches the default setting for "Max queue lifetime."
  • Queue manager message recipient limit: The maximum number of recipients held in memory by the mail transfer agent's queue manager. The default is 20000.
  • SMTP destination concurrency limit: The maximum number of parallel deliveries to the same destination. The default is 20 connections.
  • SMTP destination recipient limit: The maximum number of recipients per message. The default is 50 recipients.
  • Delay warning time: The amount of time before the sender receives the mail headers of mail that is still queued. The default is "0".

Queue monitoring

  • Queue warn threshold: The number of messages that must accumulate in the mail queue before the "Pre-filter message queue alert" is displayed as a warning on the System Status tab.
  • Queue error threshold: The number of messages that must accumulate in the mail queue before the "Pre-filter message queue alert" is displayed as an error on the System Status tab.

SMTP server settings

  • Incoming connection timeout: The time limit for sending an SMTP server response and for receiving a remote SMTP client request. The default is 300 seconds.
  • Mail filter timeout: The amount of time that the mail filter will attempt to process a message before it times out. After the specified time, the message is quarantined, and an email notification is sent to the administrator. The default is 1200 seconds. The message can be found in the quarantine by searching with the reason "Processing failure."
  • Maximum number of recipients: The maximum number of recipients that the appliance accepts per delivery request. The default is 1000.
  • Header size limit: The maximum amount of memory (in bytes) that is used to store a message header. The default is 102400.
  • Disable VRFY command: Stops some techniques used to harvest email addresses. The default is "Yes" because the appliance uses other methods to protect against directory harvest attacks.
  • Soft bounce: Continues to queue mail that would otherwise be returned to the sender. This option disables locally generated bounces, and prevents the permanent rejection of the mail. The default is No.
  • Reset to Defaults: Restores the factory settings.

After you have made any necessary changes you can:

  • Click Apply to save your changes.
  • Click Cancel to discard your changes.