Email deliverability rarely breaks all at once. It erodes over time.

Nothing looks wrong in isolation, but inbox placement starts slipping anyway.

This checklist mirrors how we approach real audits. Not as a hunt for a single broken setting, but as a system review.

The goal is not to chase perfect scores. The goal is control and predictability.

IMPORTANT:

Before completing this, be sure you go through links below and understand basics of email deliverability.

• How Email Deliverability Actually Works by Sujay Pawar
• Email best practices by Amazon
• Maintaining a positive sender reputation by Amazon

Gone through these links and educated yourself on email deliverability? 

Great. Now, please proceed ahead.

How to Use This Document

1. Copy this entire document into Google Docs.
2. Write your answers on a new line directly below each question, prefixed with “Answer:” or in blue color text so your answers are easy to find.
3. Do not skip sections. Deliverability problems usually hide in skipped parts.
4. Be honest. Do not guess. Use real data, screenshots, and links where asked.

Example of answering:

Question: Primary sending domain?
Answer: example.com

Conclusion

This checklist is designed to help you see the full picture. Not just individual settings, but how your domains, tools, lists, and sending behavior work together over time.

If any section felt uncomfortable or unclear, that’s a signal.
Those gaps are usually where deliverability problems start.

Revisit this audit whenever something changes in your email setup and run it at least quarterly. Consistency is what builds inbox trust.

When you control the system, inbox placement becomes predictable.

Read more at SureContact

Sending an email feels simple.

You write a message. You click send. It disappears and (hopefully) ends up in someone’s inbox.

But what happens after you click send is not simple at all.

Between your email tool and your audience, there’s a powerful filtering system that decides whether your email deserves to arrive in the inbox or be sent to spam or ignored entirely.

Gmail, Outlook, Yahoo and other inbox providers aren’t just delivery channels. They are guardians of the inbox. Their job is to protect users from emails they don’t want.

That’s why many teams face the same problems:

• Emails are sent but rarely opened
• Clicks and sales slowly decline
• Messages start landing in spam or promotions
• Unsubscribes increase
• Campaigns that once worked stop performing

Sending an email doesn’t guarantee visibility and deliverability isn’t a feature you turn on. 

It’s trust you earn over time.

Think of deliverability like a reputation score. Every email you send either strengthens or weakens that score. 

Inbox providers continuously update this score based on how your emails behave and how people react to them.

This guide explains email deliverability in simple language. Not just what to do, but why things work the way they do. 

If you want to apply these concepts to your own setup, use our email deliverability audit checklist to review domains, DNS, tools, lists, and sending behavior step by step.

By the end, you will understand how emails travel, how inbox providers think, why emails fail, and how to build a reliable long term email system.

1. The Email System in Simple Terms

To understand deliverability, you first need to understand who is involved in sending an email.

Every email passes through three main layers. Each layer plays a different role and controls a different part of the outcome.

Prefer to watch rather than read?

1.1 Your email app or tool

This is where the email is created.

Examples:

• A website sending notifications
• A CRM sending newsletters
• An online store sending order receipts

Your app decides:

• Who receives the email
• What the email says
• When it is sent
• How users are grouped and targeted

Most people think email problems come from their tool. In reality, your tool controls only part of what happens. 

Even the best tool cannot force Gmail or Outlook to show your email in the inbox.

1.2 The sending service (SMTP)

Your app doesn’t send emails directly to Gmail or Outlook. Instead, it uses a sending service called SMTP (Simple Mail Transfer Protocol).

Think of SMTP as the delivery company that carries your email from your app to the recipient’s inbox provider.

Examples of SMTP services:

• Amazon SES
• SendGrid
• Mailgun
• Postmark
• SMTP2Go

Simple analogy to explain SMTP: If your app writes the letter, SMTP is the courier that delivers it.

But the courier is not neutral. Inbox providers observe how reliable this courier is over time.

1.3 Inbox providers

Inbox providers include Gmail, Outlook and Yahoo.

They decide what happens to your email:

• Goes to inbox
• Goes to promotions
• Goes to spam
• Gets blocked

Your tool doesn’t decide where your email lands, inbox providers do. That’s why switching tools often doesn’t fix deliverability issues.

Inbox providers are not evaluating your tool. They are evaluating your identity, behavior, and infrastructure.

1.4 How all in one platforms like Mailchimp work

Tools like Mailchimp, HubSpot and Klaviyo combine everything into one system.

They provide:

• Email editor and automation
• Contact lists and segmentation
• Built in sending infrastructure
• Guidance for setup and monitoring

From the outside, it feels simple, write an email, click send. Behind the scenes, the same flow still exists:

Your app → sending service → inbox provider → user

The difference is that these platforms control both the tool and the sending service.

Why these platforms feel easier

All in one platforms are designed to reduce risk and complexity.

They:

• Hide technical details
• Protect shared sending systems
• Limit risky sending behavior
• Automatically slow down suspicious activity
• Enforce strict rules to protect their reputation

This makes them great for beginners and small teams.

The tradeoff

When you use an all in one platform:

• Platform level changes can affect your deliverability
• You don’t fully own your sending reputation
• All in one platforms charge a premium

That’s why, as teams grow, some choose to separate their tool from their sending service to gain more control, flexibility and long term reliability.

2. What Happens When You Send an Email

Every email follows the same journey.

Understanding this journey explains why deliverability depends on multiple factors, not just content.

2.1 Your app creates the email

Your tool prepares the message:

• Text and subject line
• Recipients
• Timing

Even if this is perfect, deliverability can still fail later.

This is why great copy doesn’t guarantee inbox placement.

2.2 The sending server IP address

Every sending server has an IP address. It’s the network address of the server that sends your email.

When Gmail evaluates your email, it looks at two identities:

• Your domain (your brand identity)
• The IP address (where the email came from)

If your domain is your brand name, your IP address is your delivery warehouse. Inbox providers build trust for both.

Important reality:

• A trusted brand with a bad sending server can still land in spam
• A good sending server with an untrusted brand can also land in spam

How trust for an IP is earned

Inbox providers watch how a sending server behaves over time:

• How many emails it sends
• How consistent the sending is
• How many emails bounce
• How many people mark emails as spam
• How people engage with emails

They aren’t just looking at numbers. They’re looking for patterns.

For example:

• Gradual growth in sending volume looks natural
• Sudden spikes look suspicious
• Stable engagement builds trust
• Sudden drops in engagement raise red flags

If a server suddenly sends huge volumes or spam emails, trust drops quickly. Recovery is slow and difficult.

Shared IP vs dedicated IP

Shared IP means many senders use the same server.

• Easier to start
• Reputation influenced by other senders
• Often safer for low volume senders

Dedicated IP means only you use the server.

• More control
• Full responsibility for reputation
• Requires careful gradual sending

A dedicated IP isn’t always better. If you send low quality mails from a dedicated IP, it can perform worse than a well managed shared IP.

What sending services actually do

Sending services do more than deliver emails, they:

• Sign emails to prove authenticity
• Manage queues and retries
• Adjust sending speed based on feedback from inbox providers
• Track bounces and complaints
• Protect server reputation

Your sending service is part of your reputation, not just a technical tool.

2.3 How inbox providers judge emails

Inbox providers do not judge emails one by one. They judge patterns.

They look at:

• Your past behavior
• Your sending server history
• How recipients react to your emails

They also compare your current behavior with your past behavior.

For example:

• If you normally send 1,000 emails per day and suddenly send 100,000, that looks risky
• If your emails normally get clicks and suddenly get none, that looks suspicious

Based on these signals, they decide whether your email deserves the inbox.

Inbox placement is not guaranteed. It is earned through consistent, trustworthy behavior.

3. The Four Questions Inbox Providers Ask

When an email arrives, inbox providers silently ask four questions that form the mental model of how deliverability works.

3.1 Are you really who you claim to be?

Inbox providers check whether your domain is allowed to send emails.

This is done using technical records like SPF, DKIM and DMARC.

These records tell inbox providers: “Yes, this server is allowed to send emails for this domain.”

Without these records, inbox providers cannot verify your identity. This makes your emails look similar to impersonation or phishing attempts.

Passing these checks proves identity but not trust.

3.2 Have you behaved well over time?

Inbox providers look at your past behavior:

• Do people open and click your emails?
• Do people complain or unsubscribe?
• Do you suddenly change volume or frequency?

Behavior matters more than configuration.

Even perfectly configured systems can lose deliverability if behavior becomes unpredictable.

3.3 Is your sending system reliable?

Inbox providers also evaluate how your sending system behaves:

• Is sending stable or chaotic?
• Are there many errors or bounces?
• Does volume change suddenly?

They also observe how your sending service responds to failures.

For example:

• Does it retry intelligently?
• Does it throttle when inbox providers slow down?

Choosing a sending service is not just a cost decision. It affects trust.

3.4 Does your email match what people expect?

Inbox providers compare:

• What users signed up for
• What you actually send
• How often you send

This is where many legitimate businesses fail.

If users sign up for product updates but start receiving aggressive promotions, inbox providers can detect it.

Expectation mismatch is one of the most underestimated causes of poor deliverability.

4. Why Deliverability Breaks

Deliverability rarely breaks for one reason alone. It’s usually the result of small issues across domains, tools, lists, and sending behavior.

That’s why we recommend running a full email deliverability audit checklist before making changes, so you can see what actually changed instead of guessing.

Most problems fall into three categories:

• Identity problems: Wrong or missing setup
• Behavior problems: Low quality lists, sudden spikes, low engagement
• System problems: Unstable sending infrastructure

A simple way to think about it:

• Did something change in how you send?
• Did something change in who you send to?
• Did something change in your sending system?

Real world examples:

• A company imports an old email list and suddenly sees spam placement
• A product launches a big campaign and sends 10x more emails than usual
• A team switches SMTP providers without warming up

Most teams try to fix deliverability by switching tools instead of understanding what actually changed.

5. How to Design a Reliable Email System

Deliverability isn’t fixed with one setting. It’s designed like a system.

5.1 Separate critical and marketing emails

Use your main domain for critical emails like login and receipts and use a separate subdomain for marketing emails.

Example of transactional emails:

• [email protected] → transactional emails
• [email protected] → receipts and invoices

Example of marketing emails:

• [email protected] → marketing campaigns
• [email protected] → newsletters

If both types of emails use the same domain reputation:

• Spam complaints from marketing emails affect transactional emails
• Password resets and login links start landing in spam
• Users stop receiving critical system emails

By separating domains, you create a safety boundary.

Marketing emails can take risks. Critical system emails should not.

Think of domains as trust boundaries. Experiments should never put essential communication at risk.

5.2 Make sure your email tools are authorized and correctly configured

Most email deliverability issues happen because email tools aren’t properly authorized at the domain level.

Every tool that sends emails from your domain must be approved in your DNS settings.

If your domain says “only Amazon SES can send emails”, but SendGrid or Gmail also sends emails, inbox providers see a mismatch.

That reduces trust and pushes emails to spam.

How email authorization actually works

When an email is sent, Gmail or Outlook checks:

• Which server sent the email
• Whether your domain allows that server (via SPF)
• Whether the email is signed correctly (via DKIM)
• Whether your domain has rules for handling failures (via DMARC)

If any of these don’t match, your emails look suspicious.

Real world example of a typical setup

Imagine your domain is: example.com

And you use multiple tools:

• Website emails → Amazon SES
• CRM campaigns → SendGrid
• Support replies → Gmail
• Newsletters → Mailchimp

If they all send emails from @example.com, then:

• Amazon SES must be added to SPF and DKIM
• SendGrid must be added to SPF and DKIM
• Gmail must be added to SPF and DKIM
• Mailchimp must be added to SPF and DKIM

If even one tool is missing, deliverability drops.

5.3 Use transactional emails to build trust

Transactional emails are messages triggered by real user actions.

Examples:

• Account creation confirmations
• Password resets
• Order confirmations
• Payment receipts
• Booking notifications
• Security alerts

They usually get high opens and clicks because users actively expect them. 

Inbox providers observe how recipients interact with your emails. 

When many users open and engage with transactional emails, inbox providers learn:

• These emails are wanted
• This sender has real users
• This domain is not random spam

Over time, this positive behavior strengthens your overall reputation.

5.4 Increase sending gradually

When you start sending emails from a new domain, a new IP, or a new provider, inbox providers don’t fully trust you yet so they treat you like an unknown sender.

Gradual sending helps you build trust step by step. Inbox providers prefer predictable behavior over sudden spikes.

Some tips:

• Start with highly engaged users: Send first to people who recently opened or clicked your emails.
• Increase volume in steps: Avoid multiplying volume overnight.
• Keep frequency stable: Don’t suddenly double how often you send emails.
• Monitor reactions: Watch bounces, complaints and engagement as you scale.

5.5 Treat your email list like an asset

Most teams treat their email list like a database. Inbox providers treat it like a signal of quality.

Your list directly affects your reputation.

If many recipients:

• Ignore your emails
• Never open them
• Mark them as spam
• Bounce because addresses are invalid

Your reputation declines, even if you never send spam.

• Regularly clean your list: Remove invalid addresses.
• Segment inactive users: Reduce frequency instead of blasting campaigns.
• Respect unsubscribes immediately: Ignored unsubscribes increase complaints.
• Prioritize engagement over volume: A smaller engaged list is more valuable than a large inactive list.

5.6 Align content with expectations

Deliverability is not only about technology, it’s also about psychology. Inbox providers try to understand whether your emails match what users expect.

Expectations are created when users:

• Sign up on your website
• Download a resource
• Create an account
• Make a purchase

At that moment, users form an implicit agreement about what kind of emails they are willing to receive.

Example:

• User signs up for product updates
• Suddenly receives daily promotional emails

From the user’s perspective, this feels unexpected. From the inbox provider’s perspective, this looks like low quality sending behavior.

• Be explicit about what users will receive: Tell users what type of emails they are signing up for.
• Keep frequency consistent: Avoid sudden changes in how often you send emails.
• Separate different types of emails: Use different lists or subdomains for different purposes.
• Match subject lines with content: Misleading subject lines damage trust quickly.

Inbox providers measure the gap between user intent and your content. The larger the gap, the lower your deliverability.

Trust is built when expectations and reality align.

6. Metrics that actually matter

Many teams track email volume and open rates, but these don’t reflect real deliverability or trust. 

Inbox providers care more about how people react to your emails than how many you send. 

Below are some key trust metrics:

1) Bounce rate
Measures how many emails fail to reach inboxes. 

Benchmarks:

• Good: < 2%
• Risky: > 5%
• Critical: > 10%

High bounce rates signal poor list quality or misconfigured domains.

2) Spam complaint rate
Measures how often recipients mark your emails as spam. 

Benchmarks:

• Good: < 0.1%
• Warning: 0.1% to 0.3%
• Dangerous: > 0.3%

Even a small increase can damage domain reputation.

3) Engagement signals
Inbox providers track whether people interact with your emails in terms of clicks and replies.

Benchmarks:

• Healthy click rate: 1% to 5%
• Reply rate for B2B emails: 0.5% to 2%

Low engagement tells Gmail and Outlook that your emails are unwanted.

A campaign sent to 100,000 users with 70 clicks and high spam complaints is not successful, it’s a warning. 

Deliverability is not about volume. It is about trust.

Deliverability as Long Term Trust

Deliverability grows like reputation. Consistent, relevant emails slowly build trust.

Irrelevant or aggressive emails destroy trust quickly.

When you understand this, deliverability stops feeling mysterious and starts feeling predictable.

Read more at SureContact

You’re not just running a website. You’re building an audience, serving customers and trying to stay connected once someone shows interest.

That’s where email should help. It should be simple to follow up, easy to understand what’s working, and closely tied to what’s happening on your site.

Instead, most setups feel fragmented. Contacts live in different tools. Forms, stores, and courses all collect data, but nothing quite lines up. 

You end up exporting lists, duplicating work, and spending time managing software instead of growing what you’re building.

That disconnect is the problem.

SureContact was built to close that gap, with email and CRM designed around how WordPress sites actually work, and how site owners actually use them.

What Is SureContact?

SureContact is a marketing CRM and email marketing platform for WordPress that actually belongs in your workflow. 

It’s one place for your customer names. One place to send emails. One place to run automations. One place to see how much your customers have spent.

No jumping between tools. No broken connections. No copying and pasting. 

Just a WordPress CRM that fits the way you work, combined with email marketing that matters.

How SureContact Works With You

One Home for All Your Customers

Right now, your customers are everywhere.

Someone: 

• Buys from your WooCommerce store, they’re in your store database. 
• Fills out a form, they’re in your form plugin. 
• Enrolls in your course, they’re in your course tool. 

Working like that, it’s often difficult to see the full picture.

With SureContact, everyone lives in one place. 

WordPress users, store customers, form submissions, course students, it all flows in automatically. 

Your marketing CRM shows you one complete record of each person. You know everything they’ve done with you. 

No hunting between tools. No missing the story.

See How Much Each Customer Has Spent

When you connect your store to SureContact, something amazing happens. You can see exactly how much money each customer has spent. All in one place.

Your marketing CRM becomes a money tracker. 

• Click on a customer and see their total purchases. 
• See which customers are your biggest spenders. 
• See which customers haven’t bought in a while. 

See patterns. Understand your business better.

Then use that information to send better emails. 

• Send special offers to your best spenders. 
• Win back customers who stopped buying. 
• Give love to people who are loyal. 

Your email marketing becomes smarter because you know the money behind each person.

Send Emails That Actually Matter

You can use your own SMTP solution to send emails. That means you’re in total control. 

• You send from your own domain. 
• Your email reputation stays yours. 
• Your delivery stays yours. 
• No vendor lock in. No restrictions on what you send.

Send campaigns. Send automations. Send sequences. Send as much as you want. No limits. Just you and your customers, talking directly.

Build Automations That Make Sense

Welcome new customers automatically, follow up when someone makes a purchase and send timely reminders if they’ve gone quiet. 

You can tag people based on what they do and shape the journey as it unfolds. 

Everything stays simple and visual, so you’re building flows you understand, with a clear reason behind every email that goes out.

What SureContact Does

Brings all your customers together in one marketing CRM, WordPress users, store customers, form submissions, course students. All in one place. 

Everything updates automatically. No manual work.

• Shows customer spending: Connect your store and see how much each person has spent. View total purchases right in their customer profile. Understand your highest value customers.
• Manages your contacts: Tag people, create lists, understand who they are. Know their history and see the full picture of each customer.
• Send unlimited emails: Bring your own SMTP. You control everything. Send campaigns. Send automations. Send sequences. No limits. No restrictions.
• Creates beautiful email marketing templates: Drag and drop. No code. Make gorgeous emails in minutes. Save what works. Use it again.
• Runs smart automations: Welcome sequences. Cart recovery. Win back campaigns. Post purchase follow ups. Triggered by what people do, not random timing.
• Connects to everything you use: Works with WooCommerce, SureCart, Easy Digital Downloads, SureForms, and more. Everything talks together. Your marketing CRM stays updated.
• Work together: Invite people to send emails and manage automations. Everyone stays aligned. 

Built for People Who Care About Their Customers

If you care about audience engagement, customer retention and building relationships, SureContact is for you.

It’s great for:

• Store owners: Recover abandoned carts. Send post purchase sequences. See which customers are your best spenders. Use that knowledge to send smarter emails.
• Solo creators: Stop using a dozen tools for email marketing and customer relationship management. One workspace. One login. One marketing CRM. Get your time back.
• Agencies: Handle many client sites with a WordPress CRM that scales. Organize customers by client. Run email marketing campaigns across multiple sites. Scale without more headaches.
• Course teachers: Send welcome sequences. Send milestone emails. Re-engage students automatically. Track customer spending across all products.
• Newsletter writers: Build real relationships with your audience using your marketing CRM. Send emails based on who they are and what they care about. See which customers support you most. Turn readers into true supporters.
• SaaS teams: Onboard, engage, and retain users with automations that respond to what they do inside your product, so every user feels guided, supported, and more likely to stay.

Why SureContact Is Different

SureContact is built by Brainstorm Force, a team that’s been part of the WordPress community for over a decade.

We live and work in the same ecosystem you do, which is why the product feels familiar from day one. 

We’ve built tools like Astra, SureCart, ZipWP, and OttoKit, so we understand how WordPress creators and businesses actually build, sell, and grow. 

That experience shapes how SureContact works, not as a generic marketing CRM, but as an email marketing and automation tool designed for the way WordPress sites are really used.

• Keeps your site fast: Cloud-based. Your WordPress database stays clean. Your site stays blazing fast. Your email marketing doesn’t slow you down.
• You control your email: Bring your own SMTP. Your domain. Your reputation. Your rules. No vendor lock-in. No one else controls your email marketing.
• Grows with you: As your audience gets bigger, nothing breaks. No new limits. No surprise fees. Simple pricing that scales fairly.
• Feels simple: No confusing menus. No endless settings. Things work the way you’d hope.

Ready to Bring Your Customers Together in One Marketing CRM?

Keep customer names, emails, automations, and spending data in a single workspace, so you can see the full picture and build relationships that actually matter. 

Everything works together in one marketing CRM designed to stay practical and usable as you grow. 

Take a look at the pricing plans and choose what fits the way you work.

Questions?

We’re here. Send us a note on our support. We actually read them and write back.

SureContact is a WordPress CRM and email marketing platform built for people who care about their customers. Let’s go build something great together.

Read more at SureContact