Setting Queue Manager Options

Important: After making changes, click Save. Stop the service , wait 5-10 seconds and restart the service.

Note: At the top of each Services page, the name of the Service, its Status (Running or Stopped), and a Start/Stop button appears. This allows you to Start or Stop individual Services from your respective web pages, as well as from the Service Administration page.

The Queue Manager service allows you to control the flow of messages through the mail queue. This service takes the place of SMTP32exe. by delivering messages to both local and remote destinations. Although the SMTP32.exe program still exists, it simply informs the Queue Manager when a message requires delivery.

Note: When sending mail, if a valid 1xx or 2xx response is not received when connecting, the Queue Manager will roll to the next MX record.

The Queue Manager regulates the SMTP32 processes (or threads) so that the maximum number is not exceeded. This ensures that an attempt is made to deliver all messages and that delivery not be delayed by being bumped to a queue run delivery on heavily loaded systems. Files are processed according to priority, with files that have had no delivery attempt being first. Files that need to be retried are then processed based on the time that they were placed in the spool .

Warning: The Queue Manager service is a component of the SMTP delivery process. Disabling the Queue Manager may stop or delay mail delivery.

Delivery Threads. Enter the total number of delivery threads that can be used to deliver messages. Each thread processes one message at a time. This option is set to 30 by default; its minimum value is 5. Since each Queue Manager thread can deliver one message, if the option is set to 30, the Queue Manager can deliver 30 messages at a time.

Caution: You may need to increase the number of SMTP processes if you have a large number of users who subscribe to list server mailing lists. If you do need to increase this value, you should do so in small increments, for, as you increase the number of SMTP processes, you increase the processing load on your mail server.

Max Retry Threads. Enter the maximum number of delivery threads that can be used simultaneously when the system retries to deliver messages in the queue. By default, this option is set to 15. The value for this option cannot be greater than the number of delivery threads and cannot be less than 2.
Listen Pipes. Enter the number of pipes that the queue manager opens in order to listen for files being dropped in the queue by other processes. This option is set to 4 by default. The minimum value for this option is 2 and the maximum is 20. The default value should be sufficient for most servers, but can be increased for better performance on busy servers. You must examine the log files to determine if you need to increase this number. If, prior to a queue run, you find log lines that say "Adding Queue file XXX," this means that the Queue Manager has found files it was not notified of before. In this case, you should increase the number of listen pipes.
Retry Timer. Enter how often, in minutes, the Queue Manager will attempt to re-deliver messages that failed to be delivered on previous queue runs. This option works in conjunction with the Tries Before Return to Sender option on the SMTP tab. This option is set to 30 minutes by default. The minimum value for this option is 10; the maximum is 120.
Daily Report Address. Enter the e-mail address to which a daily count report will be sent. If no address is entered, no report will be sent.
- Auto Restart on Failure (recommended). Click this check box to enable SMTPD32 to check the status of the Queue Manager. If it is not running, STMPD32 attempts to restart it. The event is then written to the log file. The Queue Manager status is checked every 2 minutes. If, after two checks, the Queue Manager is not running, IMail Server attempts to restart it. We recommend that you enable this option.

DNS Caching

The DNS cache is an internal cache of positive DNS queries. The cached DNS response remains active for the length of time specified in the Time to Live (TTL) for the DNS record.

Tip: We recommend enabling this option, since it improves delivery performance by caching and reusing positive queries.

Max DNS Entries. Enter the total number of entries allowed in the DNS cache. The DNS cache is a first in, first out list, so the list is updated as new DNS queries are performed. We recommend that you enter a value of 200. However, you can enter any value between 5 and 5000.
Clear Cache. Click this button to clear the DNS cache in the Queue Manager. This is usually not required. When_to_Use.htm
Enable DNS Cache. Select this check box to enable the DNS cache.

Failed Domain Skipping

Failed Domain Skipping occurs when IMail Server tries to deliver a message but cannot connect to the domain. The domain is added to a list of failed domains (known as the Skip List), and all recipients for that domain will be skipped for the amount of time entered as the Skip Time.

Tip: We recommend enabling this option, since it increases performance when many messages are destined for unreachable hosts.

Max Skip Tries. Enter the total number of entries allowed in the Skip List. This is a first in, first out list that is updated as new domains are added. We recommend entering a value of 500. However, you can enter any value between 5 and 5000.
Clear Skip List. Click this button to clear the current Skip List from memory.
Skip Time (minutes). Enter the amount of time, in minutes, that failed domains will remain in the Skip List before they are removed. Although we recommend 30, you can enter any value between 2 and 240 minutes.
Enable Domain Skipping. Select this check box to enable Failed Domain Skipping.

Save. Click to save your settings. An "Update Successful" message and the time of the update. appear.