Prolateral Consulting Ltd
Prolateral Consulting Ltd
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Setup examples

Prolateral offers primary and backup domain (DNS) services, with servers in key geographic locations providing the best service possible.


How to setup a Mail Relay in sendmail?
How to setup a SMTP Mail Relay in sendmail?


Follow the guide below to configure sendmail to use outMail as a Internet Mail Relay.

This article is written for sendmail version 8.11+ and although tested on Centos6, should be applicable for other distributions.

It already assumes your server has sendmail 8.11+ installed already, it has correctly configured access to the Internet and you have a terminal connection to your server with the necessary access rights to manage and administer sendmail.

You need to edit the /etc/mail/ file.

There should be a line like below:

dnl define(`SMART_HOST', `smtp.your.provider')dnl

The dnl stands for 'delete till new line' and so effectively comments out the whole line.  Remove the FIRST 'dnl' and space and replace the 'smtp.your.provider' with the Outmail server you were sent when you signed up. The line should look like:

define(`SMART_HOST', `mx??????')dnl

NOTE - strings in this file are started with the 'backtick' character ( ` ) and ended with the apostrophe character ( ' )

We now need to setup the authentication.

Further down the file, there are a number of lines starting with FEATURE( , we need to add a new line immediately after these that looks like: (remember to check the ` and ' )


Save the file.

Now create a new file called /etc/mail/authinfo containing the following line (replace mx??????,  USERNAME and PASSWORD with the case-sensitive credentials you were provided with):

AuthInfo:mx?????? "U:USERNAME" "P:PASSWORD"

Make sure that the hostname matches that in the file

If you don't have sendmail-cf installed, install it using:-

yum install sendmail-cf

Now you can rebuild the sendmail configuration with 

make -C /etc/mail


Summary of server details

Outgoing server

As provided in your signup email.

Outgoing server protocol


Outgoing server port

25, 465, 587, 2525 or 8025

Authentication Type

Basic Authentication, SSL and TLS supported


As provided


As provided

Uninstalling / Removing outMail

To change your outgoing SMTP server settings away from outMail simply follow the setup guide above and where asked to enter the outgoing SMTP mail server address and login credentials please use those provided to you for the service provider you are moving to.

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