I used Centos 6.8 to configure a Mail Relay.
1st step -
Install exim in your server :
yum install exim-mysql -y
Usually centos default MTA is postfix, so we need to change the default MTA to exim, with command below :
alternatives --config mta
It will bring you below selection :
There are 2 programs which provide 'mta'. Selection Command ----------------------------------------------- * 1 /usr/sbin/sendmail.postfix + 2 /usr/sbin/sendmail.exim Enter to keep the current selection[+], or type selection number:
Choose 2 to use exim as the default MTA, (I have chosen 2 in my example).
service postfix stop chkconfig postfix off service exim start chkconfig exim on
Now we need to change the exim configuration at /etc/exim/exim.conf
Change to below :
primary_hostname = acaprelay.amirulasyraf.com <- my mail relay hostname
hostlist relay_from_hosts = 127.0.0.3 : (add your mail server IP here) <- to make sure that you are allowed to relay in this server
Then find a section called "router" in the configuration and make sure the router is set as below :
dnslookup: driver = dnslookup domains = ! +local_domains transport = remote_smtp ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8 no_more
Above config will tell route all email, and send it for you to the recipient.
But we must make sure that your mail server know where to relay the server to, so you need to login to your mail server (origin server).
Then edit the exim config for smarthost as below :
smarthost: driver = manualroute domains = ! +local_domains transport = remote_smtp route_list = * acaprelay.amirulasyraf.com <- this will guide my mail server to relay email to my new Mail Relay Server no_more no_verify
After completed all above steps, try to send using your origin server to anyone.You will got the header of the email as below :
Return-Path: [email protected] Received: from *.*.*.*(LHLO ips1-mail.ipserverone.com) (*.*.*.*) by ips1-mail.ipserverone.com with LMTP; Fri, 6 Jan 2017 10:55:17 +0800 (MYT) Received: from barracuda.ipserverone.com (mail.as2.ipserverone.com [*.*.*.*]) by ips1-mail.ipserverone.com (Postfix) with ESMTP id 7EFE4516966A for <[email protected]>; Fri, 6 Jan 2017 10:55:17 +0800 (MYT) X-ASG-Debug-ID: 1483671316-068b3e1093354110001-4XlEqv Received: from acaprelay.amirulasyraf.com ([*.*.*.*]) by barracuda.ipserverone.com with ESMTP id OFtS3gY6HqFmSdZT for <[email protected]>; Fri, 06 Jan 2017 10:55:16 +0800 (MYT) X-Barracuda-Envelope-From: [email protected] X-Barracuda-Apparent-Source-IP: *.*.*.* DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=amirulasyraf.com; s=mail; h=Message-ID:From:Date:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:To; bh=1bP+QR4oOJI80qfwgQhGi2RMJffC7P++shP6eV7AOkU=; b=A01VatqmaxW7vdK620CspLLO/c3D9QzeFoO8+1YZT2JlUxPXNzRNfT44p7i6Rzf+z8DUckDiyAun1mOjGJxGcm8Q9WryiJB4RQ/SIVdl2pOcZ1zNQ+OzPH9YMfFBklSZ4PbELCi+6TjF110YPu99sz7x0053AJyS8tFPLjwUH3A=; To: [email protected] Subject: Test
As you can see above, it stated that it received from my Mail Relay (acaprelay.amirulasyraf.com).