Email Deliverability – Its Role, What Affects It and Best Practices

by Elastic Email | May 17, 2026

Every business relies on emails to nurture leads, promote campaigns, and drive sales. Truth be told, sending emails to users is more than just communication. It is a channel for fostering trust and elevating brand value through consistency.

Table of Contents

TL;DR
Role of Email Authentication
Factors Affecting Email Deliverability
Best Practices for Improving Email Deliverability
Future Trends in Email Content and Deliverability
Conclusion
FAQ

The scope of email marketing is so enormous that global revenue is projected to be $17.9 billion by 2027. No wonder every marketer wants to leverage it to achieve their goals and craft a resonating profile with the audience.

Email marketing trends help in optimizing campaigns for better deliverability and engagement. However, have you ever wondered if all your recipients receive the emails you send in their priority inbox? The answer is no! That’s because when emails are handled without an appropriate strategy, they land in the spam box or get bounced. This is where email deliverability comes to the forefront.

It is the rate at which emails sent from the server get positioned in the priority inboxes. Therefore, ignoring it will put you in a difficult position, causing all your marketing strategies to fail. Here, we have illustrated the importance of email deliverability for your business success and what can affect it. We will also present you the best practices to ensure high email deliverability rate.

TL;DR

Email deliverability is whether your messages reach the inbox rather than the spam folder, and since 2024 it is governed by published rules, not guesswork. Gmail, Yahoo and Microsoft all now set explicit requirements for anyone sending in volume, and failing them means junk placement or outright rejection regardless of how good your content is.

If you send 5,000 or more messages a day to consumer mailboxes, you must:

Authenticate with SPF, DKIM and DMARC - DMARC at minimum p=none, with the From domain aligned to either SPF or DKIM. Microsoft has rejected non-compliant mail to outlook.com, hotmail.com and live.com since 5 May 2025.
Offer one-click unsubscribe (RFC 8058) and process requests within two days.
Keep your spam complaint rate below 0.3%, and ideally under 0.1%.
Get the infrastructure right - valid forward and reverse DNS on your sending IPs, TLS for transmission, and RFC 5322-compliant headers.

Everything else - list hygiene, sending consistency, content quality, IP warm-up - still matters, but it matters on top of these requirements rather than instead of them. Send fewer than 5,000 a day and you need at least SPF or DKIM, though meeting the full list is the safer position as thresholds tighten.

Role of Email Authentication

Every email service provider or ESP tool scans emails and sends them to dedicated recipients. Since ESPs handle incoming emails, you must pay special attention to authentication and security if you want to achieve the target of higher email deliverability. After all, unauthenticated emails are usually classified as fraudulent or phishing emails and placed in the spam folder.

To further understand the importance of email verification for deliverability, read below.

Builds trust and brand reputation

Cyber crimes have skyrocketed today, and customers always remain on edge regarding the emails they receive in their mailboxes. If any email looks suspicious, the click-through and open rate take a damaging blow, thereby reducing the deliverability.

So, authenticating emails before hitting the send button is crucial if you want them to be placed in the recipient's inbox right away. This way, the ESP software program will leverage the trustworthiness of the authentication program, thereby increasing the likelihood of proper email placement.

Prevents spams

Unauthenticated emails mainly raise a red flag for ESP programs, increasing the probability of being marked as spam. The worst-case scenario is that the emails are blocked from entering the recipient's server. To avoid your email being deduced as spam, it is best to use email content optimization with the authentication system and secure it before sending it to the recipients.

Boosts customer confidence

Authenticated emails quickly boost confidence among your customers. Knowing that their data will be protected and that the content present in the email comes from a legitimate source - especially when combined with safe browsing tools like a Virtual Private Network - taking action will become easier for them.

That’s why they won’t mark the email address as spam, which will automatically help drive the deliverability and customer retention rate higher.

Factors Affecting Email Deliverability

Numerous variables must be considered while assessing today's digital ecosystem's email deliverability rate. Considering them beforehand will give you an upper hand in optimizing the action strategies and proper implementation.

The sender score rated by the ISP plays a crucial role in determining the email's deliverability. A higher score is likely to increase this rate, while a lower score might cause the email to be dismissed as spam or fraud.
Email content optimization is one of the crucial factors affecting its deliverability rate. For instance, a compelling subject line increases the sender's credibility and guarantees a higher opening rate.
Emails sent out irregularly will likely be re-routed to the spam folder. Therefore, marketers need to plan the schedule appropriately so that the emails are positioned in the correct folder to ensure higher opening and click-through rates.

Best Practices for Improving Email Deliverability

Following best practices to increase email engagement is essential to boosting any business's revenue and reaching the right audience. So, here are some best practices for you to help you improve your email deliverability:

Use authenticated email domains

A study from Deloitte proved that 91% of cybercrimes have phishing emails as the source. Therefore, verifying your email domain and using an authenticated one is an absolute priority. This is essential to protecting you from identity theft and other cyberattacks that are commonly done via email.

Most businesses leverage Domain Keys Identified Mail (DKIM) or Sender Policy Framework (SPF) to prevent becoming victims of email spoofing and falsified personification. Once you authenticate the email domains using these top-notch methods, the ISPs will consider the emails credible enough to send them to the recipient's server.

Maintain appropriate IP allocation

A study in 2023 revealed that approximately 14.3% of emails are marked as spam automatically and go missing from the recipient's inbox folder. The best way to avoid this event from occurring is by using a dedicated IP address.

When you stop using shared IP and instead focus on a dedicated or private one, your emails will have higher credibility and security regarding the ISP rating. As a result, the deliverability rate is also likely to increase tenfold.

Curate non-spammy subject lines

Another way to avoid your emails being overlooked or marked as spam is by curating a compelling and actionable subject line. According to a study, about 69% of recipients mark emails as spam because the subject lines are not genuine or look AI-generated.

That’s why you must ensure the subject lines don't have any typical spam or catchphrases, such as risk-free or eliminating your debt. If these are present, ISPs will automatically mark the emails as spam, and the deliverability rate will be significantly reduced.

Future Trends in Email Content and Deliverability

Businesses that adapt to future trends will be better positioned to reach their target audience. Here are a few trends you can follow for better email deliverability.

Focus on email engagement metrics

Marketers will curate strategies backed by email engagement metrics to drive the deliverability rate higher.

For instance, they will pay more attention to the click-through rates, email sharing rates, and spam complaints before structuring the emails, adding the subject lines, or choosing the recipients.

Use of artificial intelligence

AI and machine learning models will play a significant role in email deliverability. AI-based models will help streamline email deliverability by analyzing big data and providing in-depth reports on recipient behavior.

They will also assist marketers in predicting the optimal time for sending emails so that they don’t end up in the spam folder or get blocked by ESPs.

Conclusion

Many businesses confuse deliverability with delivery, so their strategies fail to yield generous results. Therefore, if you want the email marketing campaign to be successful, ensure the practices you adopt can put the emails in the recipient's box and not any other folder. Whether using email APIs or investing in email content optimization, the practices adopted will determine your emails' click-through and opening rates.

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FAQ

They measure two different things and are routinely confused. Delivery rate is the share of messages a receiving server accepted rather than bounced. It tells you the address existed and the server took the message. Deliverability, or inbox placement, is the share that landed in the inbox rather than the spam folder. A campaign can show a 99% delivery rate while half of it sits in spam, which is why delivery rate alone is a poor health check.What is a good email deliverability rate?

A delivery rate of 95% to 99% is the range usually cited as healthy, with 98% and above considered strong. Inbox placement is the harder and more meaningful number, and it runs well below delivery. A meaningful share of commercial email that is successfully delivered still lands in spam. Treat any sustained drop as a signal rather than noise: falling inbox placement usually reflects list quality or authentication problems that started weeks earlier.

Enforcement began on 1 February 2024 for senders of more than 5,000 messages a day to personal Gmail accounts, with Yahoo applying equivalent rules. You must:

Gmail tightened enforcement in November 2025, so non-compliant mail now faces temporary or permanent rejection rather than filtering.

Since 5 May 2025, senders of 5,000 or more messages a day to outlook.com, hotmail.com and live.com must pass SPF and DKIM and publish a DMARC record at minimum p=none, aligned with SPF or DKIM. Microsoft's enforcement is stricter than filtering. Non-compliant messages are rejected outright with 550 5.7.15 Access denied and the note that the sending domain does not meet the required authentication level. A rejected message never reaches the mailbox at all, so there is no spam folder to recover it from.

The bulk-sender thresholds do not formally apply, and a smaller sender needs at least SPF or DKIM rather than the full set. In practice you should meet the requirements anyway. The threshold is measured per day and is easy to cross with a single large campaign. The providers have tightened enforcement repeatedly since 2024, and every item on the list improves inbox placement for senders of any size. Building to the standard once is cheaper than discovering you crossed the line mid-send.

Gmail sets 0.3% as the hard limit and recommends staying below 0.1%. Email service providers apply their own, tighter thresholds on top of that, because your complaints affect shared infrastructure. Elastic Email, for example, reviews accounts at a 0.15% complaint-to-sent ratio and sends a warning from 0.05%. There is a parallel complaint-to-open measure that triggers review at 5% and warns at 1%. The practical target is an order of magnitude below the mailbox provider limit, because by the time you reach 0.3% the reputation damage is already done.

Yes. DMARC is now required by Gmail, Yahoo and Microsoft for bulk senders, and SPF plus DKIM alone is no longer sufficient. Start at p=none, which is the minimum the providers require and which monitors rather than blocks. It sends you reports without affecting delivery. Read those reports until you are confident every legitimate sending source authenticates correctly, then move to p=quarantine and eventually p=reject to stop others spoofing your domain. Moving straight to reject without a monitoring period is the usual way legitimate mail gets blocked.

It is an unsubscribe link in the message headers, defined by RFC 8058, that lets the mailbox provider show an unsubscribe control at the top of the message, so recipients can leave in one action without opening your email or loading a preference page. Bulk senders must include it and must process the request within two days. It is worth implementing well beyond compliance: the alternative for an irritated recipient is the spam button, and that costs you far more than a lost subscriber.

Passing authentication is a floor, not a guarantee. The common causes beyond it are DMARC alignment failing even though SPF and DKIM individually pass. A missing or invalid PTR record on the sending IP. A complaint rate that crossed a threshold weeks ago and is still suppressing placement. List quality, including stale addresses and spam traps. Sending volume that jumped sharply without warm-up. And engagement history, since mailbox providers weight how recipients have treated your previous mail. Work through them in that order - authentication and infrastructure first, because they are binary and checkable, then reputation and list quality.

It depends on volume and consistency, not on which is better. A dedicated IP gives you a reputation that is entirely your own. It is an advantage only if you send enough, regularly enough, to establish one. Low or sporadic volume on a dedicated IP looks unfamiliar to mailbox providers and can hurt placement. A shared IP draws on an established pool reputation maintained by your provider, which suits smaller and irregular senders. If you do move to a dedicated IP, warm it up: raise volume gradually over several weeks rather than moving your whole list at once.

As an outreach specialist, Ankita Malhotra connects and builds relationships with people. With over 4 years of experience along with communication skills, Ankita develops and implements effective outreach strategies that deliver goal-oriented results.

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