How to improve email deliverability: Best practices for 2026

You can have the right audience, a strong offer, and well-written emails. If your messages never reach the inbox, none of that matters.

Email deliverability sits behind every successful outbound programme. It influences how many people see your emails, engage with them, and ultimately become customers.

Deliverability is under more pressure as inboxes become more crowded and mailbox providers tighten their sender standards. Technical setup still matters, yet it works alongside audience quality, message relevance, and consistent sending behaviour.

Technical issues can damage deliverability quickly. Poor targeting, weak data, and messages that feel irrelevant can also create the negative engagement patterns that make inbox placement harder to maintain.

That’s why improving deliverability is also about relevance.

In this guide, we’ll explain how email deliverability works, what affects it, and the practical steps you can take to improve inbox placement in 2026.

Note: This guide focuses primarily on B2B outbound email. The technical principles apply across email programmes, but marketing and outbound teams need to interpret them differently: one protects subscriber trust at scale, while the other earns attention from the first message.

Better email deliverability starts with better-targeted outreach. Sopro combines intelligent B2B prospecting, high-quality data and managed sending to help businesses generate leads while protecting sender reputation. Explore our B2B lead generation services, or book a demo to see how Sopro can help you reach more of the right buyers in 2026.

What is email deliverability?

Email deliverability refers to your ability to reach a recipient’s inbox.

It’s often confused with email delivery, but they’re different metrics.

Email delivery measures whether a receiving mail server accepted your email.

Email deliverability measures where the email ends up afterwards. It could land in the primary inbox, the promotions tab, the spam folder, or be filtered out entirely.

For example, an email platform may report a 99% delivery rate. That doesn’t mean 99% of recipients saw the message. Some of those emails may have landed in spam folders or been filtered before the recipient ever had a chance to engage.

Why email deliverability is harder in 2026

Email providers have spent years improving their ability to identify unwanted messages.

That creates a better user experience. It also means legitimate businesses need to work harder to earn inbox placement.

Inbox providers are placing greater emphasis on sender reputation

Google, Microsoft and Yahoo all use a wide range of signals to determine whether an email deserves inbox placement.

Common signals include:

• Domain reputation
• IP reputation
• Authentication records
• Spam complaints
• Engagement rates
• Sending consistency

A strong reputation increases the likelihood of inbox placement. A poor reputation makes it harder for future emails to reach recipients, even when the content itself is relevant.

Buyers have little patience for irrelevant outreach

Deliverability is increasingly influenced by recipient behaviour.

Replies, clicks and other verified engagement signals can show that recipients find an email useful. Open data needs more caution in outbound campaigns, as privacy protections and bot activity can inflate it. Complaints and opt-outs are clearer warning signs.

This is where many businesses run into problems.

According to Sopro’s State of Prospecting 2026 research, 57% of buyers believe most sales outreach feels impersonal and irrelevant.

That matters because poor targeting creates poor engagement. Poor engagement damages deliverability.

Many teams spend significant time refining copy while paying less attention to the quality of their audience. In practice, relevance often has a greater impact on deliverability than minor copy improvements.

AI has made generic outreach easier to scale

AI has made email creation faster, but it has also made it easier for businesses to send large volumes of generic outreach.

This means there is more competition for inbox attention and greater scrutiny from inbox providers.

The businesses getting the most value from AI use it to identify better prospects, personalise outreach more effectively and remove low-fit contacts before campaigns launch.

The 12 factors that influence email deliverability

Improving deliverability comes down to a combination of technical setup, audience quality and sender behaviour.

1. Configure SPF, DKIM and DMARC correctly

Authentication helps inbox providers verify that your emails are genuine.

The three core protocols are SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail) and DMARC (Domain-based Message Authentication, Reporting and Conformance).

Together, they help prevent domain spoofing and demonstrate that your organisation follows recognised email security standards.

If these records are missing or misconfigured, deliverability issues often follow.

Google requires all senders to use SPF or DKIM. Its bulk-sender requirements also include SPF, DKIM and DMARC. For bulk mail, at least one authenticated domain must match the domain in your visible From address.

2. Protect your sender reputation

Sender reputation acts as a trust signal for inbox providers.

It is influenced by factors such as bounce rates, spam complaints, authentication status and engagement rates.

Reputation takes time to build and can deteriorate quickly if campaigns generate poor engagement or a high volume of complaints.

Monitoring reputation should be part of every email programme, particularly for businesses relying on outbound prospecting.

3. Warm up new domains gradually

A brand-new sending domain has little reputation history. If it immediately starts sending large volumes of email, inbox providers may treat that behaviour as suspicious.

Instead, increase sending activity gradually.

Start with smaller volumes, build positive engagement signals and allow inbox providers to develop trust in the domain over time.

Domain warm-up remains one of the simplest ways to reduce risk when launching a new email programme.

4. Monitor spam complaint rates

Spam complaints are among the clearest negative signals available to inbox providers, and even relatively small increases can affect inbox placement.

If complaint rates begin to rise, investigate audience targeting, email relevance, sending frequency and list quality.

Treat complaints as early warning signs rather than as a reporting metric to review retrospectively.

5. Maintain good list hygiene

Email databases naturally degrade over time, as people change jobs, organisations close accounts and contact details become outdated.

Regularly remove hard bounces, invalid addresses, duplicate contacts and long-term inactive recipients.

A smaller, healthier list usually performs better than a larger list containing poor-quality data.

6. Avoid purchased or unverified email lists

Purchased lists create multiple deliverability risks and often contain outdated contacts or invalid addresses.

Poor-quality data increases the risk of invalid addresses, low engagement and spam complaints. For outbound campaigns, build or source data around a defined audience, validate it before launch and remove contacts who are not a genuine fit.

Building targeted prospect lists takes longer, but it creates stronger engagement signals and better campaign performance over time.

One of the most interesting findings from Sopro’s research concerns targeting quality.

Our AI-powered suitability matching removed between 20% and 40% of prospects from campaign audiences. These were contacts that traditional firmographic filters identified as suitable, but unlikely to convert in practice.

The result was 356% more closed deals while lead volume stayed the same. That is a commercial outcome rather than a direct inbox-placement metric, but it shows why audience quality deserves as much attention as email infrastructure.

The lesson is that relevance drives engagement, and engagement influences deliverability.

Explore why job titles aren’t necessarily a reliable filter in our guide – What’s your real total addressable market (TAM)?

Steve Harlow at Sopro comments: “Most deliverability conversations start with DNS records and spam filters. Those things matter, but they’re rarely the root cause of poor performance. The biggest gains usually come from sending fewer emails to better-fit prospects. When relevance improves, engagement improves. When engagement improves, inbox placement tends to follow.”

7. Give recipients a clear way to opt out

For bulk marketing or subscribed email, use a one-click unsubscribe process where the mailbox provider requires it, and honour requests promptly.

For outbound campaigns, give recipients a clear way to opt out of future contact and remove them from active sequences when they do. This reduces complaints and protects your long-term sender reputation.

8. Keep send volumes consistent after warm-up

Warm-up is only the first stage. Once a domain is established, avoid sharp spikes in volume or sudden changes in cadence. Stable sending patterns give mailbox providers fewer reasons to treat activity as unusual.

Read our guide to the best time or day to send sales and marketing emails for a closer look at how timing, relevance and audience behaviour work together.

9. Monitor deliverability by mailbox provider

An overall delivery rate can mask a problem with a single provider or audience segment. 

Review performance across Gmail, Yahoo, Microsoft and other key mailbox providers, then investigate where complaint rates, bounces, or inbox placement begin to decline.

How to test email deliverability

A blended delivery rate does not tell you where individual messages land. Before a major campaign, run inbox-placement tests across Gmail, Yahoo, Microsoft and other key providers to see whether emails reach the inbox, promotions tab or spam folder.

For Gmail, use Postmaster Tools to check whether your sending domain meets Google’s sender requirements and investigate any compliance issues. Review those findings alongside bounce rates, complaint rates and reply data to work out whether the problem is technical, audience-related or linked to your sending behaviour.

10. Write emails people actually want to read

If recipients ignore your emails, delete them immediately or mark them as spam, mailbox providers take notice.

Good outreach tends to have a few things in common, like clear relevance, specific targeting, concise messaging and genuine personalisation.

Poor outreach often looks like mass marketing disguised as personal communication.

This is where poorly managed AI-assisted campaigns can fall down.

The problem is rarely the technology itself. The problem is using generic prompts that produce generic output.

As we noted in our State of Prospecting 2026 research, buyers already feel that much of the outreach they receive is impersonal. Generic AI copy reinforces that perception.

11. Keep your sending infrastructure separate

Many businesses send all email activity through the same domain and infrastructure. That creates unnecessary risk.

Transactional emails, newsletters, customer communications and outbound prospecting all have different engagement profiles.

Where volume and risk justify it, separating activities can help protect reputation. This approach limits the impact if one channel experiences deliverability issues.

12. Review deliverability regularly

Deliverability needs regular review because mailbox-provider algorithms, buyer behaviour and your own sending patterns all change over time.

What worked 12 months ago may not work today.

A regular review process should cover:

• Authentication settings
• Domain reputation
• Audience quality
• Engagement metrics
• Spam complaint rates
• Sending infrastructure
• Email content performance

Common email deliverability mistakes

The same deliverability mistakes appear repeatedly in B2B outreach programmes.

Buying email lists

Purchased data often contains:

• Outdated contacts
• Invalid addresses
• Spam traps
• People with no interest in hearing from you

Scaling too quickly

Many businesses damage their reputation during the first few weeks of a campaign by increasing volume too aggressively.

Increase volume only when bounce, complaint and engagement trends remain stable.

Treating personalisation as a first name field

Recipients are increasingly good at spotting fake personalisation.

Adding a first name does not make an email relevant.

Real personalisation comes from understanding the prospect’s situation, priorities and likely challenges.

Ignoring negative signals

Rising complaint rates, falling reply rates and a decline in verified engagement are warning signs.

Too many teams continue sending at the same volume while performance deteriorates.

Mailbox providers notice long before marketers do.

How to improve email deliverability if you’re already having problems

If deliverability has started slipping, focus on the fundamentals before making bigger changes.

Start by:

• Checking authentication records
• Removing invalid contacts
• Reducing send volume temporarily
• Monitoring complaint rates
• Reviewing targeting quality
• Improving message relevance
• Separating sending infrastructure where appropriate

Avoid quick fixes or “deliverability hacks”.

Many deliverability issues can be traced back to audience quality, sender reputation or engagement.

Why audience fit belongs in your deliverability plan

Technical setup gives your emails a fair chance of reaching the inbox. Audience quality helps protect that opportunity. 

When campaigns reach people with a genuine reason to care, they are less likely to be ignored, reported as spam or treated as noise.

Better targeting means higher relevance, more engagement, fewer complaints and stronger sender reputation.

Improve deliverability before it becomes a problem

Of course, you can always bring in the experts. Sopro has delivered over 146 million emails in the last eight years..

Poor deliverability usually begins before the send button. As a demand generation company, Sopro combines campaign-specific audience building, relevant messaging and managed sending support to help B2B teams reach the right buyers without relying on high-volume outreach. Explore our email marketing agency services, or see how our cold email marketing agency helps teams build healthier, more effective outbound campaigns.

We have expertise in various industries, including marketing and advertising lead generation, financial services lead generation, and lead generation for internet companies and broadband providers.

To see how Sopro works and discover our suite of services, book a demo or get a glimpse into how we work, with our email marketing for lead generation strategies.