Advanced Configuration

MailerQ can be configured using the "/etc/mailerq/config.txt" config file. Most of the variables and settings in this config file are discussed in separate articles. However, the following settings are not mentioned anywhere else:

max-delivertime:        86400
max-attempts:           0
retry-interval:         600,600,1800,1800,3600,3600,7200
server-id:              1
license:                /path/to/license.txt
user:                   username
lock:                   /path/to/lock.txt

Most of the settings speak for themselves. A small overview.

Max deliver time

When a mail gets greylisted, or when there is an other type of soft failure, MailerQ reschedules the mail for later delivery. Inside the JSON data of each message you can add the optional properties "maxdelivertime" and "maxattempts" that instruct MailerQ how long it should retry to deliver the message, and when it should give up trying.

If you do not include these properties, MailerQ falls back to the "max-delivertime" and "max-attempts" config file settings. The "max-delivertime" variable holds the number of seconds MailerQ should keep on trying after the message was consumed for the first time. The "max-attempts" setting holds the total number of attempts before giving up.

You should normally set the "max-attempts" value to 0, meaning unlimited. MailerQ will then only give up after the number of seconds set in the "max-delivertime" variable, no matter how many attempts are made.

Retry interval

If a mail is published back to the outbox queue to be tried again, MailerQ uses the "retries" property in the JSON to find out how long it should wait for the next attempt. Because this setting is JSON based, it is possible for each message to have its own retry interval. This could be useful if you send both transactional as well as commercial mass mailings. For transactional emails you normally want small intervals because these mails should be delivered as soon as possible.

If the "retries" property is not set in the input JSON, MailerQ falls back to the setting from the config file. The config file variable "retry-interval" is used for that. This setting should hold a comma separated list of the delays between the attempts. This should be set to a number of seconds.

The default value is "600,600,1800,1800,3600,3600,7200". This means that the second and third attempt is sent 10 minutes after the previous attempt. The next two attemps use an interval of half an hour, then an interval of one hour for the next two attempts, and all subsequent attempts are sent after three hour intervals. You can change variable to anything you want.

Server ID

Each message that is accepted by MailerQ gets a unique message ID. To prevent that two running MailerQ instances both assign exactly the same ID to a message, you can assign a "server-id" variable. This identifier guarantees that message ID's will never conflict.

server-id:      1


To work properly, MailerQ needs a license file. The license file can be downloaded from the MailerQ website. You can store the file anywhere on the file system. The path to the license file can be configured by setting

license:        <Path to your license> (empty by default)


If you have configured MailerQ to use ports lower than 1024 (like port 25 for SMTP and/or port 80 for the management console), the MTA must be started as user "root". Once the ports have been opened, MailerQ changes its identity to the user set in the config file.

user:           <user name> (empty by default)

The user name to change identify to after the SMTP and HTTP ports have been opened.


To prevent that MailerQ starts more than once, MailerQ stores its process ID (pid) in a lockfile. The name and location of the lockfile can be set in the configuration file.

lock:           <filename> (default: /tmp/

User Statistics

MailerQ sends a hourly message to Copernica. This message contains some use statistics for that hour, e.g. the number of errors that occured. This information is used to improve MailerQ. Users with a paid license can disable this message by adding the heartbeat property to the config file:

heartbeat:      false (default: true)