# 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.

### Requirement

This can only be set up on Postfix version `>=2.7.x`, because the parameter we need `sender_dependent_default_transport_maps` is available in Postfix-2.7 and later releases.

To check your Postfix version run:

    # postconf mail_version

Which would return something like: `mail_version = 2.10.3`

### Steps

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

    sender_dependent_default_transport_maps = pcre:/etc/postfix/sdd_transport.pcre

- Add file `/etc/postfix/sdd_transport.pcre` with below content. NOTE: we use domain `example.com` for example, it will use transport `sample-smtp` - see examples.

    /@example\.com$/   sample-smtp:

- Create new outgoing SMTP transports in `/etc/postfix/master.cf` like below. Note: you must replace our sample IP address `172.16.244.159` with your IP address. If you want to use IPv6 address, please use `smtp_bind_address6` instead of `smtp_bind_address` below.

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

Option `smtp_helo_name` and `syslog_name` are optional.

After this restart the Postfix service to apply your changes:

    # /etc/init.d/postfix restart

Note: any unmatched domains will continue using the server's primary IP address just as before.