E-Mail

On each server, a local Postfix instance is running to deliver mails to their destination.

SPF Record

To explicitly allow your server to send mails from a particular domain, you need to add an SPF record to your DNS zone:

example.com.              3600     IN      TXT     "v=spf1 mx a:<fqdn-or-smarthost> -all"

Note

depending on your companys guideline, servers can send mails directly or through a designated smarthost

Warning

please make sure to include all other servers that should be able to send mails from your domain as well

Configuration

Warning

changing any values can led to unintended consequences. Please make sure to plan any changes carefully and ask us for advice if you’re in doubt

mynetworks

  • list of trusted remote SMTP clients that have more privileges than strangers
  • see the Postfix documentation for details
  • default: 127.0.0.0/8 [::1]/128

relayhost

envelope_from

  • rewrite envelope from of each sent mail to the address specified
  • useful to catch any return errors at a particular mailbox without configuring all applications independently
  • default: empty (internally defaults to <username@server-domain>)

smtp_fallback_relay

  • optional list of relay hosts for SMTP destinations that can’t be found or that are unreachable
  • see the Postfix documentation for details
  • default: empty

inet_interfaces

  • network interface addresses that this mail system receives mail on
  • see the Postfix documentation for details
  • default: loopback-only (localhost Port 25)

message_size_limit

  • the maximal size in bytes of a message, including envelope information
  • see the Postfix documentation for details
  • default: 25600000 (25MB)

monitoring

  • whether our external monitoring will check the condition of the mail service on this particular server
  • default: true

smtpd_tls_cert_file

  • path to a TLS certificate used for incoming SMTP connections
  • default: empty

smtpd_tls_key_file

  • path to a TLS key used for incoming SMTP connections
  • default: empty

Example

{
  "postfix::relayhost": "example.net",
  "postfix::envelope_from": "webserver@example.net"
}