Email Marketing & AutomationMarketing Infographics

Infographic: A Guide to Troubleshooting Email Deliverability Issues

When emails bounce it can cause a lot of disruption. It’s important to get to the bottom of it – fast!

The first thing we should start with is getting an understanding of all of the elements that go into getting your email to the inbox… this includes your data cleanliness, your IP reputation, your DNS configuration (SPF and DKIM), your content, and any reporting on your email as spam.

Here’s an infographic providing a rough overview of how email goes from creation to inbox. Items that are highlighted are what impacts the likelihood of your email getting delivered to the subscriber’s inbox:

Email Deliverability Infographic - How Email Gets Delivered to the Inbox

Troubleshooting Bounce Issues

To make sure you can troubleshoot and fix problems with email deliverability quickly and efficiently, here’s a straightforward step by step guide to troubleshooting bounce issues.

Step 1: Review Your Email Log Files or Database for Bounce Codes

Check the database for the email client that is bounced the most. Look into the bounce code and see if it starts with 550 bounce code. If so, a spam filter is your problem. Asking recipients to add the email address to their contacts will possibly resolve this. If not possible, go to the next step.

Step 2: Check Your SPF, DKIM, and DMARC Configuration, DNS Settings, and Policies

This is your next step whether or not you find a 550 bounce code. Various software is available to help you complete this step:

MXToolbox Google Check MX DKIM Validator

When these measures are not set correctly it can cause email deliverability problems. Additionally, you can verify these settings by reading through your email header data – they often show you whether or not the originator passed these checks.

Step 3: Check Your IP Reputation / Sender Score

If the issue persists there may be a problem with the IP address’s reputation or sender score. Return Path (now owned by Validity) software allows you to check the IP’s sender score. If the score is not consistent this will give you some insight into the cause of the problem. This software can also help you to identify ways to improve going forward.

Step 4: Check Whether Your IP Address is Blacklisted

There are third-party services that both ISPs and mail exchange servers validate against to see whether or not they should be delivering your email to their customer’s inbox. Spamhaus is a leader in this industry. If you can provide an audit trail that you have a business relationship with the subscriber who reported you as SPAM or opt-in records, they will typically remove you from any blacklists.

Step 5: Check Your Content

Internet service providers and email clients look through the words in your email to identify the likelihood that it’s SPAM. Simply stating “Free” in a subject line or multiple times throughout your content can get your email shipped directly to the Junk folder. Most Email Service Providers will help you to score your content and remove words that could get you in trouble.

Step 6: Contact the Subscriber’s Internet Service Provider

If the sender score isn’t the issue, it may be necessary to contact the email client you identified in the first step. Deliverability issues can occur with large providers such as Gmail, Microsoft, BigPond, and Optus. However, if you identified the client to be a government email address it is best to ignore the issue as it is not possible to contact the relevant body directly.

Ask the email client service providers (Microsoft, Google, Telstra, Optus) to whitelist the IP address. This should prevent the problem from happening again. Be sure that the SPF, DKIM, and DMARC are correct before you make contact with the service providers – this will be their first question. You’ll need to prove these measures are set correctly before they can action anything.

NOTE: The Junk Folder Is Delivered

Keep in mind that a bounce means that the recipient service rejected the email and responded with that code. An email that is delivered (250 ok code) can still be sent to a Junk Folder… something you’d still have to troubleshoot. If you’re sending hundreds of thousands… or millions of messages, you’ll still want to use an inbox placement tool to troubleshoot whether or not your emails are going to the inbox or the junk folder.


Working through these steps should enable you to resolve most email send problems without difficulty. However, if you’ve completed these steps but the issue remains, help is at hand – contact our team for support.

Based on the above step by step guide, we have assisted many clients to resolve their deliverability issues. For example, for one of the Australian enterprise banks, we followed the above steps to increase deliverability from 80% to 95% in 2 months. 

Bob Croft

Bob Croft is an experience martech leader within the APAC region, working with over 15 clients in the past 8 years time across multiple industries.

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