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How to Identify & Troubleshoot Issues With Your Sender Domain

Email marketing can be difficult and confusing. There are multiple steps that you need to take in order to get started performing outreach. Even after taking all the time to prepare for an email campaign, there are still multiple factors in play that can end up sidelining your efforts and either ruining your sender domain, or wasting your time. Since there are dozens of variables involved when it comes to the process of delivering an email message to someone else, there are a lot of ways that issues can arise.


While it’s a frustrating process to try to identify problems and issues with sender domains and email addresses, there are plenty of methods for troubleshooting DNS, deliverability issues, and blacklisting issues. There are a number of free tools that are available online to assist with the process of analyzing and identifying, as well as services that can clearly lay out in simple terms what is wrong with your sender domain, why the issue is happening, and the steps you should take in order to troubleshoot it. 


In this article I want to go over some best practices regarding what you should do once you are aware of an issue with your sender domain, but not exactly sure where it’s originating from.

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How To Identify An Issue With Your Sender Domain?

Typically, if there is an issue with a sender domain or email address, you will be made aware of it pretty quickly if you are actively checking in on your email campaigns. A few indications that there may be an issue with your sender domain, your contact list, or even an issue on your email service provider's side are:

  • Failed deliveries

  • 550 spam error messages

  • Email bounce backs 


So what if the issue with your sender domain isn’t obvious? In many cases for some email users, they will not be aware an issue is occurring until someone they are attempting to contact lets them know, either because their email bounces back when they attempt to send a message to you or your email shows up as being undeliverable when verified.


Whichever way you discover an issue is present, it will need to be dealt with as soon as possible if you wish to continue any type of outreach efforts.  The reason this needs to be dealt with so urgently is because most issues related to email delivery can have a drastic effect on your deliverability rates and your sender reputation. Delivery issues that result in landing in spam or email bounces can have long term ramifications for the overall health of your sender domains.

How To Troubleshoot Issues With Your Sender Domain?

So you have identified that an issue is present with either your email address or your sender domain. Where do you go from here? Troubleshooting issues with your sender domain is a broad topic, so this article won’t cover every possible issue.  In this section I will walk through the general troubleshooting steps you should be taking when attempting to figure out an issue.

DNS/ESP Provider Issues

If you are running into issues directly with your sender domain, the issue will almost always lay with your DNS records in some way, shape or form. For email, the primary records you need to worry about are:


The MX record determines how email messages should be routed in accordance with the Simple Mail Transfer Protocol (SMTP), or in simpler terms, it shows servers which mail servers accept incoming mail for a domain and where emails sent to the domain should be routed to.


  • SPF record

A Sender Policy Framework Is an email authentication practice that is used to prevent spammers and scammers from sending spoofed email’s on behalf of your domain.


  • DKIM record

Domain Keys Identified Mail is an email authentication process that allows a mail server receiving incoming mail to verify that a specific message has actually been sent from an associated email address. DKIM exists to prevent spoofed mail, spam, or malicious emails from being received by an email server if they cannot be properly identified as coming from the actual sending domain.


  • DMARC record

Domain-based Message Authentication, Reporting & Conformance (DMARC) is a DNS protocol that uses both Sender Policy Framework, (SPF) and DomainKey Identified Mail (DKIM) to determine the authenticity of incoming and outgoing email messages coming from a domain. This protocol makes it easier for Internet Service Providers (ISPs) and receiving email servers to determine the authenticity of an email message, ensuring that spam, spoofed, or illegitimate mail is not making it through to your inbox.

These primary records are what relate directly to how email delivery works, so if any of these records are incorrectly added to the DNS of your domain, it can cause deliverability issues.


Other records under your DNS can also cause deliverability issues if they are either incorrectly added, contain broken links or lookup references, or cause conflict with other records that are utilized for the email delivery process. Identifying these issues can be incredibly tedious to do manually, so thankfully there are plenty of tools that you can utilize in order to perform a complete breakdown of the health of your DNS.


The primary tool I recommend for everyone to start with when attempting to troubleshoot delivery issues is to run their sender domain through a tool called MxToolBox. Specifically under MxToolBox, I recommend utilizing their “Domain Health” check under their Supertool section of the website, as this tool essentially combines a bunch of their other specific record checking tools into one comprehensive test.

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This test specifically will outline everything that does not comply with the generally accepted syntax of how your DNS records should be set up. To just define ‘syntax’ in this context, this term applies to what the general guidelines are for the Domain Name System and how records should be structured under a server in order to make it easier for everyone accessing these records to know what to look for.

These standards help make things easier for mail servers to connect with one another, but some of these standards do not need to 100% match what is expected, so MxToolBox will simply make you aware that these do not fit the standard guidelines by highlighting these records with a yellow indicator button.


An example of an average, healthy sender domain typically will look something like this:


Please note: I have blocked out the host addresses for security reasons, but this column will contain the actual host address that MxToolBox is throwing an error or warning about.


While there are 9 errors presented here, these are mostly syntax warnings that you wouldn’t need to worry about for standard email outreach. Some of these issues you can fix or troubleshoot yourself, but others will require you to either contact your DNS provider or ESP provider in order to fix. For each error that pops up, clicking on the blue links to the right hand side of the results will bring a more detailed explanation for why this error/warning is being thrown.

What Are Some Common Issues With Your Sender Domain?

When you run your sender domain through this tool, always be on the lookout for anything that is marked in red as a problem, as this is an indication a record is not working correctly and needs to be corrected.

Also, always be on the lookout for any type of issues being thrown by your SPF and DMARC records, since any properly setup SPF or DMARC record will not show up at all when you perform a health test on your domain, so it’s a good sign when there is no traces of these records coming up. 


To verify that your DKIM record is properly setup is a bit more difficult since it is not as easy to read DKIM records via tools such as this.  My recommendation to check if everything is properly set up is to simply send an email to yourself, then look at the email header to see if there is any mention of DKIM in it. If it is present in your email, everything is set up properly.


Any other issues marked as red will require your attention to fix or troubleshoot, so if an issue is present that you are unsure about, try reading into MxToolBox’s explanation on the error that can be found on the right hand side of each result that gets thrown.


Email issues with your sender domain can sideline entire outreach campaigns and cost you valuable time when attempting to grow your business and make new connections with your audience. While it is impossible to completely avoid deliverability issues over time, there are plenty of resources available to help isolate and resolve these issues in a quick and timely manner.

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