Email deliverability is the measure of whether your email reaches your subscribers’ inbox—whether that’s primary, social, or promotional—and avoids landing in the spam folder.

“When I think about email deliverability, I’m really thinking about whether my email reaches my subscribers,” says Carin Slater, Manager of Lifecycle Email Marketing at Litmus. “Whether it’s blocked because of my IP reputation, because an email client flagged me as spam, or because I have an outdated email address, I’m thinking about how to get my email message in front of my subscribers, in their inbox.”

Delivery vs. deliverability

Delivery and deliverability often get used interchangeably, but they’re actually two parts of the journey an email message takes to go from your ESP (email service provider) to an inbox.

• Email delivery confirms that an email was accepted by the subscriber’s mail server without bouncing.
• Email deliverability evaluates how many of those delivered emails bypass spam filters and reach their intended destination in the inbox, where subscribers are likely to engage. This is where ISPs determine whether or not your email lands in the spam filter, an extra folder like Gmail’s Promotional Tab, or the inbox.

How does email deliverability work?

Picture your local post office and how many packages they sort through every single day. That’s exactly what ISPs do for their users—your subscribers. First, your package has to be delivered. Think of your email delivery as your mail carrier literally dropping off mail in your mailbox or at your door. But deliverability is what happens after the message gets delivered. Do you sort it on your kitchen table, or does it go straight into the recycling bin? That’s email deliverability.

Every time an email pops up in your inbox, it’s because that’s where your ISP decided it should go.

How to check your email deliverability

Deliverability has long been considered a “black box” area of marketing. Where your email campaign lands is largely up to the whims of each email client’s sorting functionality—though we’ll talk about several factors that you *can* influence in a moment.

To get a complete view of your email deliverability, you need to look at both pre-send testing tools and post-send monitoring tools.

• Pre-send testing: pre-send tools allow you to address deliverability risks—like blocklist status or authentication issues—before you send. Resolving these in advance strengthens your chances of reaching the inbox.
• Post-send monitoring: post-send tools analyze inbox placement across different email providers to reveal if your emails reached the inbox or spam. Going beyond typical ESP data, these insights enable you to troubleshoot effectively and optimize future email marketing campaigns.

Using both pre-send and post-send tools provides a well-rounded approach to email deliverability, making sure each send is set up for success. In fact, marketers who describe their email programs as successful are 22% more likely than those at less successful ones to monitor their deliverability or inbox placement.

Supporting both stages of deliverability, Litmus pre-send testing tools proactively identify potential issues—like sender reputation concerns or spam-triggering content—before they impact email campaign performance. Post-send monitoring then provides insights into where your emails actually landed, helping you refine and improve future sends.

What is a good email deliverability rate?

Good benchmarks for deliverability are tricky to find because few email marketers actually measure it. 22% of email geeks who took our survey admitted they don’t measure their deliverability or aren’t sure whether or not they do. And when we analyzed thousands of emails to understand trends in deliverability, we found that 70% of emails show at least one spam-related issue. That means most email marketers you ask give a big ‘ol shrug when it comes to their deliverability rate.

Email deliverability is worth every bit of attention you give it. Here’s why prioritizing deliverability helps your marketing go the extra mile:

1. Reach your audience

For subscribers to engage with your content, they first need to see it. High deliverability means your messages reach the inbox—right where your subscribers expect them.

“Let’s say I have a list of 60,000 people. When I send an email, I want it to reach as many of those 60,000 as possible,” says Carin. “What’s the point of having 60,000 people on a list if it’s just going to go to spam and nobody’s going to see my email? That’s just wasting everybody’s time.”

2. Build trust and strengthen your brand reputation

The inbox is a personal place—one of the last digital places a person can truly “own.” When a subscriber invites you into that space, you need to treat that space with respect. According to our email friends at ZeroBounce, 78% of survey respondents said they mark an email as spam if the email “looks like spam.” Also, 54% stated they report a message as spam if the sender didn’t ask permission to email them.

You don’t want your subscribers to be googling, “Is [brand name] a scam?” If you’re in the spam folder, it automatically makes your brand seem less trustworthy. That’s why each email marketing campaign sent is an opportunity to build trust. Showing up in the inbox consistently (not the spam folder) reinforces credibility and loyalty with your audience. 

3. Maximize ROI from every campaign

Done right, email marketing is still one of the most successful marketing channels for businesses. But you’ll miss out on the $36 for every $1 spent if your emails never reach the inbox. 

Your subscribers can’t open it if they can’t see it! The more emails that reach the inbox, the more visibility and engagement you receive, boosting your ROI. 

4. Drive engagement and conversions

Improved deliverability means more eyes on your content. Each successful inbox placement strengthens your relationships with subscribers and inbox providers alike. Positive engagement signals, like opens and clicks, build credibility, improving your chances of inbox placement for future sends. Better deliverability means your emails reach more subscribers, driving traffic, engagement, and conversions with every send.

What are key metrics for email delivery?

Monitoring key metrics is essential for achieving a high deliverability rate, ensuring you make the most of your budget and effort. 

Here are the metrics to keep a close eye on:

Delivery rate:	The percentage of emails the internet service provider’s (ISP) email servers did not return or bounce.
Bounce rate:	The percentage of emails with temporary or permanent unsuccessful delivery, also known as bounced emails. There are two kinds of bounces: Hard bounces and soft bounces. Hard bounces mean the email address you’re using is invalid or expired. Soft bounces are more temporary due to email volume or a service interruption. If your email bounces, then it’s not delivered.
Spam complaint rate:	The percentage of your audience who mark an email as spam.
Open rate:	The percentage of your delivered emails that subscribers opened.
Click-through rate (CTR):	The percentage of how many people click on a call-to-action (CTA) in your email.
Unsubscribe rate:	Measures how many people opt out of your emails.
Inbox placement rate (IPR):	the percentage of your emails that make it to the inbox and not the spam folder.
Sender reputation:	a mix of factors that inbox service providers (ISPs) use to gauge whether you’re a trustworthy sender.

IP reputation—the perceived trustworthiness of the IP addresses you use for sending emails—also plays a key role in sender reputation. Building a positive IP reputation, particularly when using a new IP, requires a gradual increase in email volume, or IP warming. Following IP warming best practices helps establish trust with inbox providers, especially when transitioning to new providers or scaling up volume.

While delivery and open rates offer essential customer insights, post-send monitoring tools provide deeper visibility into inbox and spam folder placement. These tools go beyond basic ESP reports, giving you actionable insights to refine and improve future sends.

What factors affect email deliverability?

Strong email deliverability takes a proactive, strategic approach. Here are the core factors to focus on for better inbox placement and engagement:

1. Sender reputation 

Think of your sender reputation as a composite score of everything that goes into your deliver and deliverability. ISPs look at three main areas to determine your sender reputation score: 

• Sender behavior: Your email strategy doesn’t just impact your subscribers. ISPs are watching, too. Things like your email send volume and cadence can indicate spammy practices.
• Subscriber behavior: Do subscribers want to receive your emails? That’s what ISPs are evaluating. The opens, clicks, and replies you receive for your emails indicate to them that you’re a reputable sender and should get sorted into the inbox.
• Email list hygiene: Without delivery, there is no deliverability. If your emails constantly bounce (whether it’s hard bounces vs. soft bounces) or if you hit spam traps, you’re going to land in the spam folder.

“I know not everyone will open every email I send. But I want them to have the option to open it, read it, and click on it, so that means I need to do everything I can to make sure my sender reputation and domain reputation is good and that I’ve followed all of the rules from main email clients like Google, Yahoo, and Outlook,” says Carin.

2. Your email infrastructure and authentication

Proper authentication protocols verify that your emails are legitimate, reducing the chance of being flagged as spam. This tells ISPs (and by extension, your subscribers) that you are who you say you are.

There are four different email authentication protocols to choose from. 

• Sender Policy Framework (SPF) shows which IP addresses or domains that can send mail on your behalf via a DNS TXT entry. This way, mailbox providers know that if it’s sent from your company’s domain or IP address, it’s from you.
• DomainKeys Identified Mail (DKIM): DKIM matches a public and private key, like a digital signature, to associate a given email message with your organization as part of the authentication process.
• Domain Message Authentication and Reporting Conformance (DMARC): DMARC takes the most effort, but is also the most important to get right. DMARC defines how receiving inbox providers should handle messages that fail an authentication check. They can either do nothing, quarantine the email, or reject it. We strongly recommend you set your DMARC to p=reject. This is the best protection against phishing and spoofing attempts for your brand and signals that you’re trustworthy to mailbox providers.

To comply with deliverability rules from Gmail and Yahoo, you need to complete SPF, DKIM, and DMARC. 

But there’s one more authentication protocol you can add: Brand Indicators for Message Identification (BIMI). While BIMI is technically optional right now, we still recommend adding it to your email infrastructure—not only is it another layer of security, it also helps you stand out in the inbox by adding your logo. This can boost open rates by up to 21%, making your emails instantly recognizable and reassuring—but when we asked email geeks about it, only 8% use it right now. All the more reason to jump on it.

3. The number of emails you send

Mailbox providers consider email volume and send frequency to assess whether an email sender might be engaging in spammy practices.

“It’s all about consistency,” says Carin. “Spammers don’t have a regular cadence. They just randomly send emails, and a lot of them, all at once. If I send 1,000 emails, but I only send them randomly, it doesn’t look as good as 10,000 emails sent every month at the same time.”

Email volume and frequency play a significant role in deliverability. A sudden spike in the volume of emails, especially from a new IP address, looks pretty spammy to spam filters (and it will probably annoy your subscribers, too.) Establishing a positive sender reputation from a new IP or domain requires a gradual volume increase—a process known as IP warming. 

IP warming is especially valuable during transitions to new providers, rebrands, or high sending volume marketing campaigns like Black Friday, helping build trust with inbox providers and ensuring consistent inbox placement.

4. List quality and engagement

Maintaining a clean, engaged list is essential for building a good reputation with ISPs. This is not a one-and-done activity, but something that you should check in on each quarter. Regularly clean your list to remove inactive or invalid addresses and avoid spam traps—hidden addresses that catch senders with poor list hygiene. 

If someone hasn’t engaged with you in a while, you don’t have to automatically remove them. Start with a re-engagement campaign, which asks subscribers if they’d like to still hear from you. Re-engagement campaigns revive inactive subscribers, while personalization and segmentation keep content relevant, boosting engagement and signaling value to providers. We’ll talk more about how this works in the next section.

5. Email content and formatting

Content quality matters, but not in the way that you think. The era of obsessing over certain words or phrases is over. (That means yes, you can say the word “free!” in your emails again.)

“There’s so much more that goes into it than just the words you use,” says Carin. “It’s important not to overuse spammy words, of course, but what really matters is that your subscribers want to receive the emails you’re sending. That they’re actively engaging with your content. If an ISP sees that nobody’s interacting with your emails, they’re going to say, ‘Nobody wants this. Must be spam.’”

When you think about your email content, think about what your subscribers want to see. Are you meeting the email personalization trifecta of “right person, right time, right message?” There’s a reason certain phrases trip the spam filter—because they’re usually associated with emails that don’t match subscriber preferences (or are straight-up scams.)

Spam filters review everything from subject lines to formatting to assess if an email could be spam and assess overall spam rates. Litmus Spam Testing helps you stay ahead by flagging potential deliverability issues like blocklist status or unverified authentication, so each email is optimized for inbox placement.

Understanding what causes email deliverability issues empowers you to take proactive steps to improve and maintain it. Here are some key actions to consider:

1. Create an email marketing strategy that puts your subscriber needs first

Deliverability has many technical elements, and we’ll talk about those. But a lot of email marketers miss the obvious about deliverability: that if you try to force emails on people who don’t want to receive them, you won’t be successful. 

“You’re a guest in your subscriber’s inboxes, so respect what they have told you. Whether that’s their overall preferences and topics, or if they say they want their emails in Dark Mode, or they sign up for your newsletter and nothing else, you have to honor that,” says Carin.

Ask yourself, why are you sending this email in the first place? And if it’s because “so-and-so in X department asked for it,” think deeper. Says Carin, “Everyone wants to send an email, but you have to ask why. Why would a subscriber be excited to get this email in their inbox? Do they care about this? Are we sending it because we want to send something, or because people want to read it? It has to be the latter.”

2. Craft relevant and engaging email content

With subscribers spending only an average of 8.97 seconds reading an email, every element should count. That means:

• Optimizing your email envelope (subject line and preview text) to improve open rates.
• Personalizing emails and prioritizing value-driven, relevant content over overly promotional language. 
• Using clear CTAs that encourage subscribers to click or reply to your email.

It works like this: more relevant emails lead to more engagement from your subscribers. More engagement signals to mailbox providers that you’re a legitimate sender, which helps your overall sender score, and by extension, your deliverability.

3. Make emails personal 

Subscribers opt-in to receive your messages because they value your brand. 

Personalization makes subscribers feel recognized, boosting engagement, conversions, and loyalty. 

Engage subscribers with tactics like:

• Combine segmentation and personalization to align with where subscribers are in their journey, tailoring future messages based on their interests.
• Use dynamic content to populate messages with product recommendations, exclusive offers, or relevant weather-based updates.
• Engage subscribers with interactive elements, like polls or surveys, to make your emails more engaging and valuable.

That’s why investing in a strong personalization strategy is so important. Sending personalized emails that speak to your subscriber’s interests—whether that’s a retail category or specific topics they want to hear more about—will go a long way toward helping your deliverability.

4. Maintain a clean and engaged email mailing list

Regular email list hygiene ensures you’re only reaching interested, valid contacts, which reduces the chances of hitting spam traps. That means you need to evaluate your email list on a regular basis to remove invalid emails, including those who have bounced.

The key metric to look at when evaluating your list, besides delivery rate, is engagement. If someone hasn’t opened, clicked, replied, shared, or otherwise engaged with your email…do they actually want to get your emails? 

At Litmus, we use a quarantine system with email addresses that seem inactive. “If they start interacting, they leave the quarantine list and go back into the regular email flow. But if it’s more than 90 days and they still haven’t touched one of our emails, we mark them as unsubscribed. It’s much better to have a smaller, highly engaged email list than a larger one full of random email addresses for deliverability,” says Carin.

Your email list is a fundamental aspect of your email deliverability, so don’t skip this step. 

5. Use double opt-in (DOI)

One way to keep your email list clean is to proactively screen potential subscribers for engagement. For years, double opt-in got laughed at for introducing friction into the process—but it’s this friction that keeps typos, spam traps, and bots from your list.

Double opt-ins verify subscribers’ intent to receive your emails, strengthening list quality and accuracy. This extra step can help reduce spam complaints and keep your list cleaner before you start getting bounces.

At Litmus, we use a mix of single and double opt-ins—double for higher-volume pages to filter out bot accounts, and single for lower-risk content pages.

6. Avoid spam traps

One of the worst things that can happen for your deliverability is to accidentally hit a spam trap. Spam traps and blocklists help inbox providers catch unwanted emails. 

• Spam traps identify senders with poor list management.
• Blocklists flag domains and IPs associated with spam. 

This is exactly why we recommend never, ever, ever buying an email list. You never know what’s lurking on a list like that! It’s not worth the hit to your deliverability just to say you have an email list over a certain number. You can identify spam traps using email deliverability tools like Litmus Spam Testing. This allows you to identify and remove problematic addresses before sending, reducing risks to your deliverability. 

7. Run re-engagement campaigns for inactive subscribers

Engagement is a big part of deliverability, so keeping your engagement high is important. During the quarantine period for inactive contacts, send them a re-engagement email. Here’s an example of one we send at Litmus (hopefully you haven’t received this! 😉)

Carin says, “Send a traditional re-engagement email at the 60 day mark for any subscribers that are not interacting with your emails, asking them directly if they still want to receive emails from you. If they still haven’t interacted after that, then we mark them as unsubscribed. That way, at least we’ve double checked that they’re truly inactive.”

8. Honor your unsubscribes

Subscribers are so over too many emails. According to our friends at Optimove, 70% have unsubscribed from at least three brands in the last three months due to email overload, and 36% have quit six or more brands. You must, must, must include an unsubscribe link.

It’s illegal under privacy laws like GDPR and CAN-SPAM to “forget” to unsubscribe someone from your list. Even if it was allowed, it’s the right thing to do to let those that unsubscribe from you go. Because you know what they’ll do if you keep sending them emails? Hit that spam complaint button so fast.  49% of survey respondents said they will submit a spam complaint if marketing emails don’t give them a way to unsubscribe, according to ZeroBounce. 

“Yes, your list sizes might go down as you clean up your email list,” says Carin. “But your engagement will go up. Instead of sending to 60,000 people that may or may not care what you have to say, you’re going to send to 30,000 people that definitely want to hear from you, and that’s super valuable.”

9. Check your sender reputation

Your sender reputation directly influences inbox placement. It’s not a set metric—it fluctuates over time based on your subscriber behavior, sender behavior, and the health of your email list.

Regularly monitor key metrics like domain and IP reputation, and use pre-send testing tools to proactively spot potential issues like blocklists or spam complaints before they impact deliverability.

10. Implement proper email authentication protocols

Without proper email authentication, your deliverability can’t get better.

Email authentication shows inbox providers that your emails are legitimate, improving deliverability by reducing the chance they’ll be flagged as spam. SPF, DKIM, and DMARC confirm your email’s authenticity, while BIMI builds brand trust and visibility by displaying your logo in supported inboxes. Authentication also protects your audience from phishing and spoofing risks.

11. Monitor feedback loops

Email feedback loops provide insights into how your campaigns perform post-send, helping you fine-tune your strategy. Regularly review these metrics with your team to quickly adapt to trends and address emerging deliverability challenges.

12. Conduct pre-send testing with Email Guardian

Confirming that authentication protocols are properly configured before sending is essential. Litmus’ Email Guardian offers 24/7 automated monitoring to verify your SPF, DKIM, and DMARC records, alerting you to authentication issues that could disrupt inbox placement. 

Proactive monitoring through Email Guardian’s automation maintains your sender reputation, helping meet evolving sender requirements from major providers like Google (Gmail) and Yahoo, and keeping your emails out of the spam folder.

After sending, post-send tools track where emails land—whether they’re delivered to the inbox or spam folder. These insights reveal engagement rates like opens and clicks, showing trends and pinpointing areas for improvement. Post-send tools also offer deeper insights into placement across different providers, providing a complete view of your emails’ journey and supporting ongoing deliverability success.

Testing your deliverability is less about specific emails and more about the behind-the-scenes of your overall email strategy. Running an email deliverability test is easy with Deliverability Monitoring from Litmus. Here’s how it works:

1. First, turn on Deliverability Monitoring by navigating to the Deliverability tab from the Monitor tab in your account’s top-level navigation and adding your unique seed address to your Email Service Provider subscriber lists.
2. Then, select the domain you want to monitor, if you have more than one.
3. Once you’re ready to go, start with Sender Authentication. This monitors your authentication protocols to make sure you’re up-to-date.
4. Once you’ve run that check, Reputation Monitoring checks your sending domain against 60+ blocklists. If your domain or IP is blocklisted, even transactional emails like password resets or purchase confirmations may not be delivered, so it’s important to see if you’ve hit any.
5. As your deliverability changes, you’ll see alerts or action items on your Deliverability Monitoring dashboard.

Pre-send tools flag potential deliverability obstacles before you hit send. These tools spot blockers such as blocklists, authentication errors, and content likely to trigger spam filters, optimizing your emails for inbox placement from the outset. Catching issues early reduces deliverability risks and increases the chances your emails land in subscribers’ inboxes.

At Litmus, we’re big fans of previewing your email ahead of time to make sure it looks great. But you can also run a spam filter test before your email goes out with Litmus Spam Testing for peace of mind. Here’s how it works:

1. Select the Test your email button dropdown on either the Home or Emails page and find the option to Start a spam test.
2. Once you select Start a spam test, you’ll see two different options, Pull from your ESP and Manual Send. 
   1. Starting a spam test with an ESP connection requires an existing ESP integration. Once that integration is in place, spam testing starts with the same Start a new spam test button. Select Pull from your ESP, choose your ESP and an email, and then the Start your test button. The test results Summary window will appear as your results begin to process.
   2. The manual send option provides you a unique list of seed addresses for each test. Use all the seed addresses that appear in the list and send your email from your ESP. 
3. Select Results in the left menu pane to see the detailed list for each test, including Authentication Filters, Blocklist Filters and Placement Filters.

You can also run a Spam Filter Test directly in Litmus Previews in the Spam Testing section of your Previews & QA for each email draft.

Still have deliverability questions? We’re here to help.

What is a good email deliverability rate?

Not to be dramatic, but a good email deliverability rate is 100%. You want as many of your subscribers as possible to see your email in the inbox.

What happens if I am blocklisted?

A blocklist (also known as a blacklist) is a list of IP addresses and/or sending domains kept by each mailbox provider of known malicious spammers. If you land on one of these by mistake, it can negatively affect your deliverability. Consider it a wake-up call to change your deliverability practices, and submit an unblock request asap. For more tips, check out our article on what to do if you’ve been blocklisted.

Can I send cold emails without damaging my sender reputation?

Yes, you can send cold emails without damaging your sender reputation. But you need to be careful with this—about how many you send, and how targeted they are. Fix your poor sender reputation first if you’re having deliverability issues.

There’s a difference between emailing every email address you can find and a well thought-out cold outreach campaign from your sales team. Make sure you’re only emailing prospects that fit your ideal customer profile, and that you offer them an opt-out option.

Why do some of my emails land in Gmail’s Promotions tab instead of the Primary inbox?

Gmail’s Promotions Tab is designed to separate email marketing campaigns from messages from friends and family. So you actually belong in the Promotions tab! Of course, it would be great to land in the inbox every time—and you can run an email campaign asking Gmail subscribers to mark you for the Primary Inbox—but if you’re landing in Promotions, you’re exactly where your Gmail subscribers will be looking for you.

What’s the difference between IP reputation and domain reputation in email deliverability?

Your IP reputation and your domain reputation are both important aspects of your email deliverability, but they’re slightly different:

• IP reputation: Your IP reputation is attributed to an IP address based on what metrics an inbox service provider (ISP) has historically seen from that IP address and how users engage with mail that originates from it.
• Domain reputation: Because email isn’t always sent from just one IP address or provider, ISPs also use your sending domain to track reputation. That allows a receiver to accumulate a reputation score across the board.

Should I use a dedicated IP address or a shared IP address for better deliverability?

In general, a dedicated IP is better for deliverability. That’s because you’re the only one in charge of your IP, which means you’re more in control of how and where it’s used. However, there are pros and cons of both shared IPs and dedicated IPs. For example, if you consistently have a high send volume, a dedicated IP will give you more control over your reputation. If your send volume has fluctuations, though, a shared IP will be better to smooth out send volume and prevent raising any deliverability red flags.

Why are my open rates dropping suddenly?

Open rates can drop suddenly for a variety of reasons. First, check your delivery rates. If something about your sending domain or email list is going awry, you’ll see it there. Then, look at inbox placement to see if you’re landing in the spam folder. If your email deliverability looks okay, then it’s time to think about your overall list management and your inbox envelope: Subject line, preheader text, and “from” name.

Does sending time affect inbox placement?

By itself, sending time does not directly impact your inbox placement. Over time, however, sending time can help you optimize for engagement, which does affect your inbox placement. The more your subscribers engage with your emails, the better your deliverability.

Deliverability is vital to a healthy email marketing program. When emails don’t reach the inbox, your efforts and marketing dollars are less effective.