8 Brilliant Ways To Troubleshoot Email Deliverability Issues

Do you know about 14.5 Bn spam emails sent every day, only 15% of the global email volumes are legitimate?

If your customers mark your emails as spam, that’s really not a good sign for your reputation and deliverability. When that happens, any future emails you send to other subscribers might end up in the spam folder too.

But, if you are following the right framework and industry acceptable recommended practices, email deliverability will give you amazing results in your overall email strategy & business revenue.

To put it in simple words, if you want to avoid sending spam, set clear expectations for your customers about the email content you send. Then, deliver on that promise and drive value & engagement.

Deliverability is half art & science but more of a habit and requires common sense. That’s why most of the brand marketers get stuck in implementing a solid email marketing strategy for their business because of: 1) email deliverability not been taken care of 2) they’re afraid. Afraid of losing the most important thing. No! It is not the money. It’s the attention. Because attention is the most precious thing right now.

Businesses, entrepreneurs and marketers are fighting to get the attention of their audience. And they are afraid of losing people’s attention. That’s why they sell right at the beginning. When attention is still super-duper high.

In their welcome email and even subsequent emails that they send out to new email subscribers, each email links to the sales page. That’s what most marketers and brands do. And that’s why email marketing doesn’t work for them. It’s what I call hope marketing. You hope for the sales to happen.

Brand marketers forget that we (consumers) buy from people. From people, we have a relationship with. And email marketing well done is your best option to build that relationship with your audience. That’s the purpose of email marketing. If you fail to deliver the wanted content, they will unsubscribe or mark you as spam, eventually creates deliverability issues.

Having said that, let us try to look at email deliverability with these 2 possible approaches:

- Working with the ISPs and sending emails as per recommended practices by each ISP
- Working against the ISPs by trying to fool spam filters and try to bypass with cheap tricks
Working with ISPs demands 2 kinds of emails — wanted by the subscriber & expected by the subscriber. Wanted type content demands value whereas expected type content demands both value and content subscribed by them.

ISPs have not defined any hard & fast rule to segregate between wanted and expected type content but they have their smart brains to gauge how well your content is serving the end recipient. The most important criteria which ISPs follow in simpler terms — engagement and complaints and of course there are other thousands of factors involved — like technical setup, authentication, domain/IP reputation, history of the domain, DNS setup, sending practices, content, 3rd party impact, and alike.

On the other hand, working against ISPs involves certain gimmicks, cheap tricks to bypass spam filters which spammers tend to follow. Practices like burning domains, IPs, harvesting the purchased data and batch & blast approach to generate leads, and alike.

And, when ISPs start penalizing you by filtering your email, there are two ways you can react:

• Examine your email campaigns and programs, and find out the root cause of what is causing complaints or spam-trap hits, and then deploy the remedy plan which is defined by ISPs

• Or, easiest way that you can go for is to avoid addressing the root causes of high complaints or low engagement, and instead focus on employing cheap tricks. For example, using lots of IP addresses to avoid scrutiny, changing domain names, or putting the entire email content in an image to avoid content filters.

There is a lot of bad email deliverability advice out there, so there are a lot of people that end up going down this path with the best of intentions. The problem is that these approaches rely on gimmicks rather than best practices. ISPs have dedicated teams of very smart people that are working to figure out the technical tricks that people use to avoid their filters and then block those tricks so that they no longer work.

For example, the three specific techniques listed above are well-known, and the ISPs have specific countermeasures that detect these techniques and penalize them accordingly.

It’s common to see things like 0.1% open ratios when using this a track two approach. And it’s common to see the “solution” to a low open ratio to be “just send more email.” The goal is often to reach the Bulk folder instead of the Inbox.

That’s why it’s very important to understand the science behind deliverability, what are the key influencers of email deliverability (and there are other factors depending upon which ISP you are talking about):

- Bounces
- Complaints
- Volume & Consistency
- Spam Traps
- Engagement

Bounces: There are two types of bounces

– Hard Bounces — Invalid Recipients/Unknown User Attempts and are indicative of list hygiene issues and may lead to bulking or blocking

– Soft Bounces — are email addresses that are refusing mail temporarily

Spikes in hard bounces or complaint rates signal deliverability problems

– Hard bounces are a predictor of spam trap hits; this means distribution contains many old addresses

– 2% recommended overall bounce rate (soft bounces and hard bounce combined)

– 1% recommended hard bounce rate, abnormal soft bounce rate spikes (over typical averages) may indicate reputation-related bulking or blocking


– Indicate end users are not expecting to receive your messages, are fatigued, or were not properly opted-in

– 0.01% recommended an overall complaint rate or lower

*Complaints are based on abuse reports received from the ISPs currently offering feedback loops

Feedback Loops (FBLs)

– A feedback loop is a system in which the ISP provides us feedback from their users who no longer wish to receive future mailings; users click the “Spam or “Junk” button, which generates feedback.

Volume & Consistency:

– ISP filters are configured to automatically monitor for any unusual activity to protect their users from spam

– Sending inconsistent volumes and/or irregular volume patterns over time can trigger spam filters and damage overall deliverability

– Senders must deliver at least 150k messages per month in order to establish and maintain a sender reputation on a dedicated IP

Spam Traps:

– Spam trap hits can be one of the most damaging issues for email deliverability and maintaining proper list hygiene is very important to avoiding spam traps.

– This requires monitoring engagement levels and removing inactive subscribers. At the very least remove all subscribers who have not opened or clicked within the past 12 months.

– Beyond 12 months, many ISPs will invalidate inactive addresses, or convert them to spam traps directly. Some ISPs will convert inactive addresses to spam traps after as little as 6–9 months of inactivity.


Recipient actions that contribute to the positive engagement quotient are:

– Clicking through links

– Adding an address to their contacts or address book

– Enabling images

– Opening and/or scrolling through the message

Recipient actions that contribute to the negative engagement quotient are:

– Reporting as spam

– Deleting the message

– Moving the message to trash

– Marking messages as read

– Ignoring messages

Now, you understand the science, you must also know how to avoid hitting spam filters or troubleshoot deliverability by following these 8 pro tips to achieve your deliverability & reputation health back to high:

Check & investigate the data source: 

Email is all about data. And, the 1st step to troubleshoot deliverability is by looking at the data source (how is it acquired, how old is the data, how engaged is the data, any segmentation done, engagement rates on the data and alike). This will give you the direct symptoms like hitting spam traps (
depending on the scenario → If data is acquired or purchased, then chances are high that acquisition source is poor, leading to hitting pristine spam traps and/or if there are poor list handling & hygiene issues, then it simply leads to hitting recycled spam traps)
Ensure email infrastructure & domains are set up correctly:

Right email infrastructure and set up plays a very important role in deliverability. Even if, you have the right data acquisition practices, engaging content to send to your customers but your domains and servers are not set up properly, it’s going to be difficult to reach your customer’s inboxes. We have seen most of the ecommerce brands & ESPs follow a practice of buying a new domain (a.k.a using a secondary domain similar to the main domain), setting that up and start mailing from the new domain (For e.g. example.com is the main domain, example.in is the new related domain). There’s nothing harm in doing that but it’s quite riskier and cumbersome to build a good reputation on that new domain, because it has a neutral/no reputation history and ISPs keep a close watch on such domains (P.S: You can still warm-up that neutral domain but it may take a longer time than usual to scale up your email volumes and building up the reputation).
We would recommend you to set up different sub-domains on the main domain (Top-Level Domain) based on messaging types (promotional, triggered, transactional) and creates sender addresses accordingly to send email campaigns. (For e.g. if example.com is the main domain, then em.example.com will be the sub-domain).
Why sub-domains? Because it gets a pseudo reputation effect from the main domain which makes the warmup easier and you can ramp up the volumes if you follow the plan and ensure high engagement rates while controlling spam complaints and bounces.
Split the messaging into separate sub-domains:

It’s always good and recommended to use different sub-domains for different messaging streams so that deliverability issues would not hamper the entire mailing process at a large scale and makes it difficult for you to troubleshoot as well. Keep promotional, triggered, and transactional-based messaging on different sub-domains. For e.g. promo.example.com can be used for marketing/promotional emails, trans.example.com for transactional and triggered.example.com for triggered messaging.
Authenticate your email with SPF, DKIM, and DMARC:

Behind every email message there are settings that tell the mailbox provider who you are and if your messages can be trusted. The two most common authentication methods are Domain Keys Identified Mail (DKIM) and Sender Policy Frameworks (SPF). SPF allows senders to tell ISPs which IPs are able to send on their behalf. DKIM allows ISPs to verify that the content sent is what the original sender intended. There is also a third authentication tool called DMARC (Domain-based Message Authentication, Reporting, and Conformance) which works by equipping email recipients with the ability to determine if an email has originated from a legitimate sender. Correct authentication is an important starting point for establishing a positive reputation with the ISPs.
Avoid Hitting Spam Traps:

Spam trap hits can damage the reputation and deliverability if you fail to implement the right email acquisition practices (Permission based Double Opt-in is recommended) and proper list handling and hygiene practices (Basic & Advanced Segmentation for segregating active and inactive). This requires monitoring engagement levels and removing inactive subscribers. At the very least remove all subscribers who have not opened or clicked within the past 12 months. Beyond 12 months, many ISPs will invalidate inactive addresses, or convert them to spam traps directly. Some ISPs will convert inactive addresses to spam traps after as little as 6–9 months of inactivity.

There are basically 2 types of major spam traps:
1) Pristine: This type of spam trap is the most dangerous as there is no way an ethical email marketer who practices double opt-in will ever encounter them. This means anyone who sends an email to these addresses will definitely be a spammer who has either scraped these emails off some website or bought the mailing list from someone who did. To avoid hitting this spamtrap, implement a permission-based double optin framework where the user will be triggered an email and he has to confirm before getting subscribed to emails.
2) Recycled: They are very old email addresses that are no longer in use by the original owner. The address has been abandoned for so long the provider has repurposed it as a trap to expose, and block emails from senders who are not responsibly managing their email marketing program. This kind of spam traps generally happens when there are poor list handling and hygiene practices and the brand keeps targeting in batch and blast. To avoid this to happen, a proper re-engagement strategy should be there to re-activate users from going dormant by sending engaging content at a controlled frequency.
Avoid using spammy content and keywords in the subject line:

Even if you have the right setup, valid/opt-in database but the content is not as per hygiene practices, it may lead to deliverability issues. Avoid using short URLs like bit.ly and spammy keywords, emoticons, and punctuations like FREE FREE FREE, !!!!!, etc. Emoticons 🔥🤩🦸🏻‍♂️ too are risky to use as they are treated as special characters or punctuation by ISPs depending on the engagement of users. These may trigger spam filters or may not so it’s advisable to test on multiple seed email ids (Test email accounts created on Gmail, Yahoo, Outlook — If you have more Gmail share in your database, create more Gmail seeds and so on) to check the landing before deploying any email campaign. If more seeds get the test campaign in the inbox, it’s highly likely that actual would land in inbox too and vice versa.
Monitor your engagement, reputation, and deliverability metrics:

We have seen most of the ecommerce brands have a limited view on metrics required for tracking deliverability and reputation. Do not limit yourself to just open rates. It’s always good to track the engagement, deliverability & reputation KPIs holistically to derive at a point whether the campaign is successful or a failure. We work with our partner who brings a new 360-degree view at looking email campaign performance by going deep what’s happening at an ISP level.

So, it’s important to monitor important key metrics like open rates, click rates, click-to-open rates, hard bounce rates, soft bounce rates, unsubscribe rates, complaint rates, delivered rates, inbox placement rates, throttling rates, read+delete rates, delete rates, blacklist, SNDS, domain reputation, IP reputation, spam rates, encryption, authentication (SPF, DKIM, DMARC), delivery errors, spam trap hits, feedback loops.
Content Optimization:

Content plays an important role in deliverability. ISPs like Gmail even cache the layout, keywords, and content type. If a brand is using image-based emails and facing deliverability issues, it’s good to try a TEXT version and with fewer URLs (not more than 3) to recover from the challenge and gradually mix it up with a good ratio of text to image 60% TEXT: 40% Image. Personalize your content. Avoid using single image-based emails because ISPs & spam filters treat such messages as less trustworthy. Don’t use short URLs (Bit.Ly or Tiny.Ly). Place URLs on only the most clicked areas. Avoid using unclear or spam flagging subject lines. Educate your customers and subscribers to whitelist your From email address, include an “Add us to your address book” link in every campaign you send. Include an email preview link in your headers. Always place your unsubscribe link prominently by highlighting the word Unsubscribe. Include physical mailing address for your business in the footer of your template.

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Inboxing Maestro is an email marketing & deliverability consulting company, that helps permission-focused ecommerce brands send better emails, get emails to the inbox & turn emails into a major revenue source.

Disclaimer: We'll show you the strategies & tactics that can help you to improve your deliverability, email performance, and ROI. Results may vary from individual to individual and company to company. Your results will be impacted by numerous factors not limited to your experience, background, discipline & time you commit to applying the strategies. We strongly recommend you follow email marketing & deliverability best practices end to end, and you should be able to achieve better results. However, we do not guarantee 100% results considering ISP's spam filters getting updated almost every day and your business decisions, you might experience some inconsistencies in your deliverability or reputation impact. We advise you to keep following the best practices and tweak the strategies; their filters will understand and adapt.

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