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Send out email from specified IP address

If you have multiple IP addresses available on your iRedMail server, and would like to send from different IP Addresses for different domains, follow the steps below.

Requirements

• Postfix version 2.7.x or later releases are required.

Configuration

• Create new transport in /etc/postfix/master.cf like below:

  • Replace IP address 172.16.244.159 by your real IP address.
  • For IPv6 address, use smtp_bind_address6 instead of smtp_bind_address.
  • Arguments smtp_helo_name and syslog_name are optional.

sample-smtp     unix -       -       n       -       -       smtp
    -o smtp_bind_address=172.16.244.159
#    -o smtp_helo_name=example.com
#    -o syslog_name=postfix/sample-smtp

Use case 1: Force all users under local domain to send out from specified IP address

You have email domain name example.com hosted on iRedMail server, and you want to force all emails sent by users under example.com to be sent from specified IP address.

• Add Postfix setting sender_dependent_default_transport_maps to the end of /etc/postfix/main.cf like below:

sender_dependent_default_transport_maps = hash:/etc/postfix/sdd_transport

• Create file /etc/postfix/sdd_transport with content below (Replace example.com by your real local domain name):

@example.com   sample-smtp:

• Run postmap and reload Posfix service to load changed settings:

postmap /etc/postfix/sdd_transport
postfix reload

Use case 2: Sent to certain recipient domains from specified IP address

You want to force all emails sent from iRedMail server to Gmail (gmail.com) to be sent from specified IP address.

• Add recipient domain name (gmail.com) and transport name in /etc/postfix/transport like below:

gmail.com sample-smtp:

You may want to force for all sub-domain names (e.g. x.gmail.com, y.gmail.com) too:

.gmail.com sample-smtp:

• Run postmap and reload Posfix service to load changed settings:

postmap /etc/postfix/transport
postfix reload