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Exim Smarthost authentication – Easy Way to do it!

Are you searching for methods for Exim smarthost authentication?

Usually, smart host authentication prevents server abuse and keep the mail server IP address clean.

At Bobcares, we often receive requests to add Smarthost as part of our Server Management Services.

Today, let’s check this topic in detail and see how our Support Engineers do it easily.


About Exim Smarthost authentication

As we all know, communication through emails has become a fundamental part of our day to day life. And, Mail Transfer Agent like Exim has a major role in the sending reputation of the email server.

Exim, the popular MTA, uses the Smarthost for the quick delivery of the emails.

And, Smarthost unlike SMTP relay, is intelligent enough to relay an email onto the right place.

The Smarthost server sits between the sender’s outgoing server and the recipient’s incoming server.  The authentication feature in the Smarthost makes it more preferable.

So, if we need to send high volumes of emails regularly, it is necessary to use Smarthost. It delivers the emails smartly and avoids blacklists along the way. However, if there is no way to authenticate a user, even hackers can misuse it. That’s where the importance of enabling authentication comes.


How we enable Smarthost authentication?

As we have already said, we use Smarthost for the easy delivery of the emails.

Recently, one of our customers approached us with a query. He wanted to set up Exim Smarthost to authenticate the users.

Our Support Engineers helped him with his requirements to set up authentication.


Exim Smarthost setup

The first step is to enable the SmartHost server in the Exim configuration. Luckily there are options to enable it from the control panel or using the command line.

To do the Smarthost setup from WHM, we

Log into WHM. Then, we go into Mail, Exim Configuration, and then search for SmartHost support in Basic Settings.

In the text box put in the following, replacing X.X.X.X with the IP address or the hostname of the SmartHost server.


Similarly, in the command-line method, we configure the hostname or IP of the smart host server in the Exim configuration file at /etc/exim.conf.local 

route_list = *


Enabling Authentication

Then, we reconfigure Exim. This again depends on the type of server. In an Ubuntu server, we use the below command.

sudo dpkg-reconfigure exim4-config

Here, we choose the option “select mail sent by smarthost”.

The password file in Exim, passwd.client allows configuring a list of credentials associated with each smarthost.

So, select mail sent by the Smarthost and edit the /etc/exim4/passwd.client file and add the entries in the format:

For instance, for a domain say, with email user as and password as 1234, we add the entry

Therefore, through these steps, we can configure Exim to send authenticated emails through a Smarthost.

[Need more assistance to set up Exim Smarthost authentication? We’re available 24/7 to help you.]



In short, Exim Smarthost authentication prevents server abuse and keep the mail server IPs clean. In today’s article, we have discussed this topic in detail and saw how our Support Engineers set it up for our customers.


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