How to create a smarthost route list for a set of domains instead of all domains

Introduction

When there is a requirement to send a single domain or a particular set of domains to a configured smarthost the smarthost route_list needs to be set to read a file instead of using an asterisk as a wild card.

Procedure

Create a file using the following to set the proper permissions, user, and group.

touch /etc/smartdomains
chgrp mail /etc/smartdomains
chmod 640 /etc/smartdomains

Then modify /etc/smartdomains and add the domains that will use the smarthost with each domain on a single line. Save the file.

Next create the smarthost configuration. If using a 3rd party mail serveice provider there will be authentication invlolved and likely requires a more elaborate configuration.

The following support document has links to 3rd party configurations as a reference. Constructing the smarthost router and transport for Exim would need to be provided by the 3rd party or by an obtained qualified server administrator. These links also provides where the changes need to be made in WHM. That document is located at: How to configure a third-party smarthost

The route_list line is what needs to be adjusted to read the /etc/smartdomains file created earlier and that line would be:

route_list = ${lookup{$domain}lsearch{/etc/smartdomains}} mail.serviceprovider.biz::587

The "mail.serviceprovider.biz" portion needs to be replaced with the server provided by the mail service provider and the 587 port set to the port provided as well.