How to improve email deliverability: Tips and best practices

Email deliverability is the ability of emails to reach subscribers’ inboxes instead of getting filtered into spam or blocked before delivery. Improving it leads to better inbox placement, stronger sender reputation, and more reliable results from every campaign.

A strong deliverability setup depends on three things working together: the technical signals that prove your emails are legitimate, the list quality and message quality that keep engagement healthy, and the ongoing monitoring that helps you catch problems early.

When those pieces stay aligned, mailbox providers are more likely to trust your domain and keep your emails visible.

Improve email deliverability in five steps:

1. Authenticate the domain with SPF, DKIM, and DMARC so mailbox providers can verify that emails come from a trusted source.
2. Clean and maintain the email list to remove invalid, inactive, and risky addresses that hurt deliverability.
3. Optimize email content and design so messages look credible, read clearly, and avoid common spam triggers.
4. Monitor performance metrics like bounce rate, opens, clicks, and spam complaints to spot deliverability issues before they grow.
5. Build sender reputation gradually through consistent sending practices and proper IP or domain warm-up, especially when using new infrastructure.

1. Authenticate your emails with SPF, DKIM, and DMARC

Email authentication verifies that a message is indeed from the domain it claims to be from. Since email systems were not originally built with strong identity checks, a server could claim almost any sending address, and receiving servers had limited ways to verify that claim.

Authentication protocols solve this problem by attaching verifiable signals to each message. These signals allow receiving servers to confirm who sent the email and whether the message arrived unchanged.

SPF, DKIM, and DMARC work together to confirm sender identity, protect message integrity, and prevent attackers from sending messages that impersonate your domain.

Each protocol protects a different part of the process.

SPF, or Sender Policy Framework, verifies whether the server that sent the email is allowed to send messages for your domain.

When a receiving server gets an email, it checks the sending server’s IP address against the list defined in the domain’s SPF record. If the address appears in the record, the message passes the check. If it does not appear, the message fails authentication.

SPF is configured through a TXT record in your DNS settings. This record lists all services that send emails using your domain. That often includes your email provider, marketing tools, support platforms, and website applications that send transactional messages.

A basic SPF record looks like this:

v=spf1 include:_spf.google.com include:mailgun.org ~all

• v=spf1 – declares the SPF version
• include: – authorizes external email services
• ~all – soft-fails all other sources

A domain must have only one SPF record. Multiple SPF records cause validation errors because receiving servers cannot determine which rule set to apply. If multiple services send mail for your domain, their authorization entries must be combined into a single record.

DKIM, which stands for DomainKeys Identified Mail, verifies that the email content has not been modified during delivery. Instead of checking the sending server, DKIM adds a cryptographic signature to every outgoing message.

The sending server signs the message with a private key. The receiving server retrieves the matching public key from your DNS records and verifies the signature. If the signature matches, the receiving server confirms that the message content arrived intact.

Most email services generate DKIM keys and the required DKIM record automatically. The setup process starts in the email provider’s dashboard, where the platform creates a key pair and provides a DNS record containing the public key. You add that record to your DNS zone and enable DKIM signing inside the service.

A DKIM DNS record usually looks like this:

selector1._domainkey.example.com TXT
v=DKIM1; k=rsa; p=PUBLIC_KEY

The selector identifies which key the service uses when signing messages. The _domainkey namespace signals that the record belongs to the DKIM system. The value following p= contains the public key used for signature verification.

DMARC, or Domain-based Message Authentication, Reporting, and Conformance, adds policy and visibility on top of SPF and DKIM. It instructs receiving servers how to handle messages that fail authentication and provides reports that show how your domain is used across the email ecosystem.

DMARC also introduces alignment, which verifies that the domain used by SPF or DKIM matches the domain shown in the visible “From” address. This prevents attackers from passing authentication with one domain while impersonating another.

DMARC is configured through another DNS TXT record. A basic record looks like this:

v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com

The key parts of the record include:

• v=DMARC1 – DMARC protocol version
• p=policy – action taken when authentication fails
• rua – email address that receives DMARC reports

DMARC policies follow a clear progression.

The safest deployment strategy begins with p=none so you can observe authentication reports. Once all legitimate sending services pass SPF or DKIM checks, the policy can move to quarantine and eventually reject emails that fail authentication.

After publishing authentication records, testing the configuration is essential. Small syntax errors, missing services, or incorrect selectors frequently break authentication even when the DNS records appear correct.

Several widely used tools simplify this process, including:

• MXToolbox – checks DNS records and verifies SPF, DKIM, and DMARC configuration.
• Google Admin Toolbox CheckMX – analyzes a domain’s email setup and identifies common configuration errors.
• Mail Tester – allows you to send a test message and immediately see authentication results.
• DMARC monitoring services (DMARCian, EasyDMARC) – collect and interpret DMARC reports so you can see which systems send email using your domain.

Most authentication problems come from a small number of configuration mistakes:

• Multiple SPF records – Publishing separate SPF records instead of combining them into a single record causes validation errors for receiving servers.
• Unauthorized third-party senders – Forgetting to authorize services that send email on your behalf, such as marketing platforms or CRM systems, causes SPF authentication failures.
• DKIM selector mismatch – DKIM failures occur when the selector in the DNS record does not match the selector used by the email service. Copying the exact record provided by the service avoids this issue.
• Premature DMARC enforcement – Enabling a reject policy too early can block legitimate email if some systems are not yet authenticated. Starting with monitoring (p=none) allows you to identify every sending source before enforcement begins.

2. Clean and maintain your email list regularly

Regular email list cleaning removes invalid, inactive, and risky addresses that damage deliverability. A well-maintained list reduces bounce rates, prevents spam complaints, and helps email providers trust your sending reputation.

Email providers evaluate every campaign you send. High bounce rates, repeated sends to inactive users, or hits on spam traps signal poor list management. Once those signals accumulate, mail providers begin filtering your messages into spam folders or blocking them entirely.

List hygiene solves this problem by ensuring that your emails reach real people who actually want to receive them.

The first step is identifying addresses that should no longer receive emails. Invalid addresses generate hard bounces because the mailbox does not exist. These addresses must be removed immediately after the first bounce.

Continuing to send messages to nonexistent accounts signals careless sending behavior.

Inactive subscribers create a different problem. The mailbox exists, but the recipient never opens or interacts with your emails. Over time, these contacts reduce engagement metrics, which lowers sender reputation.

Spam traps pose the highest risk. These addresses are planted by mailbox providers and anti-spam organizations to detect senders who use purchased or poorly maintained lists. Sending messages to spam traps signals that the list was not collected responsibly or has not been cleaned for a long time.

A reliable cleaning process removes these problems and addresses them before they harm deliverability.

Most email platforms include built-in list management features that automatically suppress hard bounces and unsubscribed contacts.

Common email verification services include ZeroBounce, NeverBounce, and Bouncer. These platforms scan lists and flag problematic entries by verifying domain validity, mailbox status, disposable email services, and known spam-trap indicators.

Running a verification scan before large campaigns prevents many deliverability problems.

Automation also improves list hygiene. Many email platforms allow you to create suppression rules that automatically remove contacts after repeated bounces or long periods of inactivity. A common rule removes subscribers who have not opened or clicked any messages in the past six to twelve months.

Cleaning your list regularly improves more than technical deliverability metrics. It also ensures that your campaigns reach people who actually want to hear from you. Sending fewer emails to more engaged recipients often produces better results than sending large campaigns to disengaged lists.

Segmentation helps maintain that engagement. Instead of sending identical messages to every subscriber, segmentation groups recipients based on behavior, interests, or activity level.

Common segmentation strategies include:

• Engagement segments – active subscribers who frequently open or click emails.
• Recent subscribers – users who joined the list within the past few weeks.
• Inactive subscribers — contacts who have not interacted with recent campaigns.
• Customer segments — groups based on purchase history or product interest.

These segments allow you to tailor campaigns to different audiences. Highly engaged users can receive frequent updates, while inactive subscribers might receive re-engagement campaigns designed to confirm whether they still want to remain on the list.

List maintenance works best as an ongoing process rather than a one-time cleanup. Regular verification scans, automated suppression rules, and engagement-based segmentation keep your list healthy as it grows.

3. Optimize email content and design for deliverability

Email content and design influence whether a message reaches the inbox or the spam folder. Clear structure, balanced formatting, and responsible messaging help spam filters recognize your emails as legitimate communication rather than suspicious or low-quality traffic.

Spam filters evaluate both technical signals and the content inside a message. Even when authentication is configured correctly, poorly structured emails or misleading wording can trigger filtering rules.

Content patterns that increase the risk of spam filtering include:

• Image-heavy emails with little text. Messages that contain mostly images and very little text resemble common spam campaigns because filters cannot easily analyze image content.
• Missing or unclear message context. Emails that do not clearly explain their purpose often appear suspicious to filtering systems.
• Excessive capitalization or promotional language. Aggressive wording, like “BUY NOW” or “LIMITED TIME OFFER!!!” often triggers spam filters.
• Misleading subject lines. Subject lines that promise something different from the message content reduce trust and increase spam complaints.

Maintaining a balanced text-to-image ratio helps avoid these issues. Images should support the message rather than replace it. Important details such as offers, instructions, or calls to action should always appear as readable text.

Subject lines influence deliverability and engagement. A clear subject line explains what the email contains and sets accurate expectations. Short, descriptive wording helps recipients recognize the message’s value before opening it.

For instance, “Your April account report is ready” communicates the purpose of the email more clearly than “Important update inside.”

Personalization strengthens engagement signals. Messages that reference the subscriber’s name, activity, or interests feel more relevant and encourage interaction. Higher engagement signals tell mailbox providers that recipients value the messages you send.

Design quality also affects how email providers evaluate campaigns. Most emails are now opened on mobile devices, so messages must display correctly on smaller screens. Responsive layouts, readable fonts, and clear spacing make emails easier to read and interact with.

The table below summarizes the best design practices that improve usability and deliverability.

Transparency is another important signal for both users and email providers. Every email should clearly identify the sender and provide an easy way to unsubscribe. Legitimate senders make it simple for recipients to stop receiving messages if they choose.

A visible unsubscribe link reduces frustration and lowers the chance that recipients report the message as spam. Including accurate contact information also reinforces trust and signals responsible sending practices.

When clear messaging, balanced formatting, and accessible design work together, email providers receive strong quality signals. These signals support your authentication setup and help your messages reach the inbox consistently.

4. Monitor your email performance metrics closely

Monitoring email performance metrics reveals how mailbox providers and recipients respond to your messages. These metrics show whether emails reach the inbox, whether recipients engage with them, and whether deliverability problems are emerging.

Email deliverability rarely fails without warning. Changes in engagement patterns, bounce rates, or spam complaints often appear long before messages start landing in spam folders.

Tracking these signals helps you identify issues early and correct them before they damage your sender reputation.

Several core metrics provide the clearest picture of your email performance:

• Bounce rate – percentage of emails that could not be delivered.
• Open rate – percentage of recipients who open the email.
• Click-through rate – percentage of recipients who click a link in the email.
• Spam complaint rate – percentage of recipients who report the email as spam.

Bounce rate is one of the most important indicators of list health. A high bounce rate usually means the mailing list contains invalid or outdated addresses. Hard bounces occur when an address no longer exists, while soft bounces indicate temporary delivery problems, such as a full mailbox or server issue.

Open rate reflects how many recipients view the email after it arrives in their inboxes. A sudden drop in open rates can signal that messages are being filtered into spam folders or that subject lines no longer capture attention.

Click-through rate measures how many recipients click links in the email. This metric shows whether the message content matches subscriber expectations and whether the call to action encourages engagement.

Spam complaint rate is another critical signal. When recipients mark emails as spam, mailbox providers treat the sender as potentially harmful. Even a small increase in complaint rate can quickly damage deliverability.

Looking at these metrics together provides a clearer picture than reviewing them individually. For example, a campaign with low open rates but normal bounce rates may indicate poor subject lines.

High bounce rates, combined with rising spam complaints, point to problems with list quality.

Most email platforms provide built-in dashboards that track these metrics automatically. Services such as Mailchimp, SendGrid, and HubSpot display real-time campaign performance and highlight unusual changes in engagement.

Dedicated monitoring tools offer deeper insight into deliverability performance. Platforms such as GlockApps and Postmark allow senders to test inbox placement and monitor sender reputation across multiple mailbox providers.

Setting up alert systems makes monitoring more effective. Many email platforms support notifications when key metrics exceed defined thresholds. For example, you might receive an alert if bounce rates exceed a certain percentage or if spam complaints increase after a campaign.

These alerts allow you to pause campaigns and investigate the cause before additional messages affect your reputation.

Consistent monitoring turns deliverability management into a proactive process. Instead of reacting after problems appear, you can detect early warning signs and correct them before inbox placement begins to decline.

5. Maintain a positive sender reputation and IP warm-up

Sender reputation measures how trustworthy your domain and sending infrastructure appear to mailbox providers. A strong reputation improves inbox placement, while a poor reputation causes messages to be filtered into spam folders or blocked entirely.

Mailbox providers evaluate reputation by analyzing sending behavior and recipient engagement. Consistent sending patterns, low bounce rates, and positive engagement signals indicate responsible email practices.

High complaint rates, large numbers of invalid addresses, or sudden spikes in sending volume create the opposite signal.

Several factors influence sender reputation:

• Engagement levels. High open rates and clicks signal that recipients value your emails.
• Spam complaints. When recipients mark messages as spam, mailbox providers treat the sender as potentially harmful.
• Bounce rates. Frequent delivery failures indicate poor list quality.
• Sending consistency. Sudden increases in volume often trigger filtering systems.

Maintaining stable sending behavior helps build trust with mailbox providers over time. Sudden changes in campaign size or frequency can appear suspicious, especially if the sending domain or IP address is new.

IP warm-up solves this problem by gradually introducing your sending activity. Instead of sending thousands of emails immediately, you begin with small campaigns and slowly increase the volume over time. This allows mailbox providers to observe normal sending patterns and positive engagement signals.

A typical warm-up sequence might look like this:

This gradual approach helps mailbox providers establish trust in the new sending infrastructure. Sending large volumes immediately from a new IP address often triggers spam filters because the sending behavior appears abnormal.

Feedback loops provide another important signal for managing reputation. Many mailbox providers offer feedback loop programs that notify senders when recipients mark messages as spam. These reports help identify which subscribers or campaigns generate complaints.

Removing or suppressing addresses that generate spam complaints prevents repeated negative signals.

Compliance with anti-spam regulations also supports a healthy sender reputation. Regulations such as CAN-SPAM and GDPR require senders to provide clear identification, accurate subject lines, and easy unsubscribe options.

Following these rules demonstrates responsible email practices and reduces complaint rates.

Recipient engagement ultimately plays the largest role in maintaining sender reputation. Mailbox providers prioritize messages that recipients open, read, and interact with regularly. Campaigns sent to engaged audiences strengthen reputation signals, while large sends to inactive contacts weaken them.

Using a dedicated business email domain instead of free mailbox providers also strengthens the sender’s reputation. Professional email hosting platforms such as Hostinger Business Email build credibility with professional email hosting through secure domain-based mailboxes, built-in spam protection, and stable email infrastructure that help maintain consistency.

Why email deliverability matters for your business

Email deliverability determines whether your messages actually reach the inbox. If emails are filtered into spam folders or blocked entirely, campaigns lose visibility, engagement drops, and the return from your email marketing investment declines.

Strong deliverability supports several core outcomes for your business:

• Marketing ROI protection – Email marketing delivers an average $36 return for every $1 spent, making it one of the highest-ROI marketing channels. If messages fail to reach the inbox, that potential revenue disappears before subscribers even see the campaign.
• Engagement opportunities preservation – The average email open rate across industries is about 35.6%, which means a large portion of subscribers are willing to engage with email when they receive it. Deliverability ensures those engagement opportunities are not lost to spam filtering.
• Core marketing channel reliability – 78% of marketers use email as part of their multichannel strategy, making it a core communication tool for campaigns, product updates, and customer engagement. Poor deliverability weakens one of the most widely used marketing channels.
• Mobile engagement improvement – Over 60% of email opens happen on mobile devices, and responsive email design can increase unique mobile clicks by 15%. Reliable inbox placement ensures these mobile-first audiences actually see and interact with your messages.
• Long-term customer relationship support – Email remains one of the most consistent ways to communicate with customers, with 93% of consumers using email daily. When emails reliably reach the inbox, businesses maintain continuous contact through newsletters, promotions, and service messages.

Deliverability is not just a technical detail. It determines whether email can function as a reliable revenue channel and a consistent communication system for your customers.

How email deliverability supports your email marketing strategy

Even the best-written email campaign fails if the message never reaches the inbox. Deliverability determines whether subscribers actually see your emails, which directly affects engagement, conversions, and overall marketing ROI.

When deliverability is strong, every stage of your email marketing program works more effectively. Campaign planning becomes more reliable because you can trust that messages will reach the intended audience.

Engagement metrics such as opens, clicks, and replies reflect real subscriber interest rather than inbox filtering issues.

Deliverability also supports conversion-focused messaging. Promotions, product launches, onboarding emails, and lifecycle campaigns depend on timely delivery to influence customer decisions.

If those messages are filtered or delayed, the campaign loses momentum and potential revenue.

Over time, good deliverability strengthens list growth and retention as well. Subscribers consistently receive newsletters, updates, and offers they signed up for, which builds familiarity and trust with your brand. That steady communication helps maintain long-term engagement and reduces churn.

Deliverability should always be treated as an ongoing process rather than a one-time setup. Regular monitoring, list maintenance, and responsible sending practices ensure that technical reliability supports long-term marketing performance.

Once your deliverability foundation is in place, the next step is building a complete email marketing strategy that aligns campaigns, segmentation, and content with your business goals.

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