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How to improve email deliverability? Get your SPF, DKIM, and DMARC in order

Posted by HostAsean Editor on 27 05 2019. in Web Hosting

Improve your email deliverability: SPF, DKIM, and DMARC

Getting your legitimate email to reach your recipient’s inbox is a much bigger challenge than it sounds. We have to take extra measures to improve our email deliverability and show that our legitimate emails are valid so that receiving servers can easily identify the good from the much larger volume of bad spam emails.

The good news is that our cPanel based web hosting clients will typically have these essential email validation methods set automatically. SPF and DKIM are the first two things to set and check to ensure your emails reach your recipient’s inbox. Relative newcomer DMARC is also becoming more popular and every little helps, but it is not set up automatically.

What are SPF, DKIM, and DMARC?

All of these are set in your DNS settings. In cPanel this can be found in the “Zone Editor”, but be careful and don’t change anything you aren’t sure of – changing the wrong things here can make your website and email inaccessible.

SPF, or “Sender Policy Framework”, basically identifies the trusted sources that can send email for your domain name. This helps prevent anyone hijacking your name to send spam mail from their own servers.

DKIM, or “DomainKeys Identified Mail”, is similar to SPF. It is a digital signature issued by the sending server, and if it matches it shows that the message originated from a valid source.

DMARC, or the lengthy “Domain-based Message Authentication, Reporting & Conformance”  is slightly different. It is an extension of SPF and DKIM, and adds reporting functionality so you can see what percentage of messages you send are valid. Another use of DMARC is to instruct mail servers how to handle the email depending on the pass or fail status.

How can I check my email deliverability?

Our favourite tool is the “Port 25” validator. It couldn’t be easier to use – just send a blank email to check-auth@nullverifier.port25.com and wait a few minutes for the automatic reply. It’ll contain some data including lines showing if you passed or failed the SPF and DKIM checks. If it’s all good it’ll show like this:

==========================================================

Summary of Results

==========================================================

SPF check:          pass

“iprev” check:      pass

DKIM check:         pass

SpamAssassin check: ham

Another useful tool is mail-tester.com (https://www.mail-tester.com/). Just visit the site and send an email to the unique address shown, then check your score. This is a more in-depth check where you can send an actual email since sometimes it’s your email content that is triggering a spam filter.

Where do you set up SPF, DKIM, and DMARC?

Before setting these up, you should have a basic understanding of DNS records. Otherwise please ask us for help.

SPF & DKIM
cPanel makes SPF and DKIM easy. You can find the options under the “Email Deliverability” icon. It should already be set up and configured correctly, but it will show an alert here if there are any problems.

DMARC
To set up DMARC we recommend the free service from Postmark, which you can find here: http://dmarc.postmarkapp.com. Just follow the instructions to add the new DNS record.

It’ll send weekly reports to the email address specified which can be useful to monitor your email deliverability.

Third-party DNS services
If you manage your DNS manually on a third-party service such as on CloudFlare, then you’ll need to set or edit your records manually. We’ll assume you know what you’re doing here. For SPF and DKIM it is usually just a case of copying the exact DNS records shown in cPanel to create or update a TXT record on your third-party service.


We hope that helps improve your email deliverability. Are you looking for more email tricks and tips? Have a look at our other blog posts about email troubleshooting or contact us if you have any questions about your email and web hosting account.

HostAsean Editor
HostAsean Editor
Website Editor at Host Asean Ltd.
Our team post tips, tricks and interesting news on the HostAsean blog and like to keep up to date with news from the tech industry and the ASEAN region where we are based. Subscribe for the latest updates or check back regularly.

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