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Jump To: Support > KB > NetManager > Email > AdvancedSettings

Advanced settings to customise delivery methods

The following are settings that can be made in the NetManager configuration file.


mail_relay defines the upstream SMTP server to send external mail via. If left empty, email will be delivered directly. The format is [user:pass@]server[:port] so any of the following are acceptable:

  • (e.g.
  • server:port (e.g.
  • username:password@server (e.g.

If using Gmail, create a user similar to with known password. Then set mail_relay to


mail_source defines the local IP address to use when sending email. Normally, the main external IP address will be used, but if you have multiple addresses, you may want to pick one explicitly.


mail_smtplisten defines the local IP addresses and ports to listen for incoming mail on (format one of <IP>, <port> or <IP:port>). Normally, port 25 (and 587) will be listened on all IP address, but you may want to listen on a non-standard port


mail_maxrecipients is used to limit the maximum number of recipients per transmitted message. If not set, an email to multiple recipients on the same server will be sent as one message with multiple recipients. If set, the message will be sent multiple times to a smaller number of recipients. This can be used to work around limitations from some email providers who erroneously use this optimisation as a spam indicator (e.g. Google and BT)


mail_maxmessages is used to limit the number of messages sent in a single SMTP connection. Normally a connection will be reused when possible to reduce load on all parties, but some incorrectly configured mail servers may view this with suspicion.


mail_externalname sets the name that the mail server reports itself as when an external server connects in. Normally, this defaults to the main email domain.


mail_local_domain sets the domain to use if a mail is sent without specifying a full domain (e.g. system mails get sent by root, using this option makes them get sent by root@your.mail.domain instead of root@your.internal.domain). Normally this will be set by domain_external, but this also makes the NetManager accept mail for that domain too. If you want NetManager to just relay mail for your mail domain use mail_local_domain instead of domain_external.


mail_forcedomain allows you to rewrite all outgoing mail so that it has a fixed domain name, irrespective of what the mail client tries to use. The domain will be either domain_external or mail_local_domain.


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Page last modified on November 16, 2018, at 10:44 AM by sborrill