October 27, 2023

Maximizing Email Deliverability: What Affects It + How to Improve

Discover all you need to know about email deliverability – affecting factors, effective strategies, and emerging industry trends.

Maximizing Email Deliverability: What Affects It + How to Improve

Email deliverability is not just about bounces it’s a measure of how often your emails land in your recipient’s inbox without being filtered into the spam or junk folder.

Whether you're an SDR aiming to reach more prospects or a SaaS platform looking to garner more sales, email deliverability is critical for your success.

In this article, we’ll discuss what email deliverability is, the seven factors affecting it, and 10 practical tips to bolster your deliverability efforts. We’ll also look at three emerging industry trends and share an effective tool to improve your deliverability.

Let’s dive in!

This Article Contains

What Is Email Deliverability?

Email deliverability signals how many of your emails get delivered to your recipient’s primary inbox instead of the spam folder. 

It’s measured as a percentage of emails (out of your total sent emails) your recipients’ internet service provider (ISP) accepts. 

Email Deliverability Rate = Number of delivered emailsTotal number of sent emails x 100 

1. What Is a Good Email Deliverability Rate?

Ideally, you’d want all your emails to reach your recipient, but a deliverability rate of 95% and above is good.

While you can manage a few factors that determine your deliverability rate, there are also affecting factors like your recipient’s inbox being full, which are out of your control.

It’s important to note that most sending platforms will only show you how many of your emails bounce (meaning they get rejected from the inbox). However, this doesn’t account for emails landing in spam/junk folders which the recipient won’t see. 

2. Why Does Email Deliverability Matter?

Email deliverability rates point out if your emails are reaching their intended audience. In case you fail to reach the right inboxes, your subsequent marketing email campaigns may suffer and wind up in spam. 

This undermines your deliverability and dents your sender reputation in the long run.

3. How to Track Your Email Deliverability?

Email deliverability monitoring is vital to measure the success of your email campaign. 

The process involves tracking where specifically inside the inbox your email landed. Almost all major email software platforms offer specific built-in analytics you can access (which is usually only based on bounce, open and click rates). But you can obtain a more comprehensive picture with email deliverability tools like Allegrow which track how often your email traffic is filtered into spam.

7 Key Factors Affecting Your Email Deliverability

Here are the seven factors influencing your email deliverability:

1. Sender Reputation 

Email servers assign a sender score to you depending on the quality of your past email campaigns. If many recipients mark your emails as spam, or if your messages bounce back from unvalidated email addresses, your sender reputation declines, undermining your email deliverability. 

Besides sender reputation, email deliverability also relies on:   

  • Domain Reputation: It’s the reputation your domain earns from an email service provider based on how recipients engage with your emails. If more contacts open and respond to your emails, you earn a positive domain reputation, and if more prospects tag your email as spam, your domain reputation declines.
  • IP Address Reputation: It measures how well an IP address behaves. If an IP address sends genuine, spam-free emails, it earns a positive IP reputation, and if it’s associated with malware and bulk spam mail, it gets a negative IP reputation.

2. Email Authentication

Email authentication is setting up authentication protocols to ensure the email service provider that you’re the one sending the outreach emails and they can be trusted. 

The three major authentication protocols are:

  • SPF (Sender Policy Framework): The Sender Policy Framework protects you and your recipients from spam and spoofing. It enables you to add a list of senders authorized to send email from your domain.

    For instance, using separate email APIs or software tools for your marketing and sales emails, you can add both services as approved senders using an SPF record. This lets your contacts know that the messages are authentic and trustworthy.
  • DKIM (DomainKeys Identified Mail): DKIM uses digital signatures and encryption keys to validate your emails and prevent recipients from replying to illegitimate messages.
  • DMARC (Domain-based Message Authentication Reporting & Conformance): DMARC adds an extra layer of security to your emails – an alignment test. It also lets you warn recipient servers about a failed email test so that they can discard or quarantine a suspicious email. 

3. Email List Quality  

The quality of your prospect list is pivotal to boosting your email deliverability.

If your list comprises outdated email addresses or typos, your outbound emails will be rejected by recipient servers and bounced back. Additionally, if you continue emailing unengaged contacts who mark your messages as spam, you risk being tagged a spammer.

Both instances are examples of an unhealthy email list that impacts your deliverability.

4. Email Volume and Frequency

Spammers usually send blasts of emails to recipients from a new domain before the recipient mailbox provider can identify and block them. 

When you start your outreach campaign from a fresh domain, sending bulk emails can trigger a spam filter. 

Instead, start by sending a small volume of messages at regular intervals to build up your reputation. Maintain the cadence during your initial cold emailing days and gradually increase the number of emails.

Besides email volume, the frequency of sending them also affects deliverability. Email frequency is not fixed and evolves as you build your sender reputation. Start with a low frequency of emails and then increase it depending on prospect engagement.

5. Email Subject Line and Content 

Most recipients will open your email depending on its subject line. A misleading or clickbait-y subject line can turn off readers and trigger them to mark your messages as spam. 

An email service provider like Gmail can even identify spammy keywords in your subject line and send your emails to spam.

Besides your subject line, your email’s content must also be free of spammy words to get past most spam filters. Sending emails with spammy subject lines or content dents your sender reputation and ultimately reduces your email deliverability.

6. Email Engagement Metrics

You can assess the success of your email campaign using three key metrics:

  • Spam Complaint Rate: It’s the number of emails recipients mark as spam out of all your outbound messages. The industry-acceptable spam rate is 0.1%.  Anything above that will lower your deliverability.
  • Bounce Rate: It’s the percentage of your emails that bounce back or are rejected by recipients. This usually happens when you email a risky contact, which could be invalid, a spam trap or someone with a very strong filter on incoming email. (you’ll want this rate to be below 2.8% for cold emails). 
  • Response Rate: It’s a metric of the number of emails that receive a response out of the total emails sent. A good response rate is around 10%, but in some segments, 5% might be a reasonable target.

  • Inbox Placement Rate: It’s the percentage of outbound emails that reach a prospect’s primary inbox out of your total outgoing emails. (meaning they didn’t land in spam or junk folders). You’ll want this to be above 90%. 
  • Open Rate: It’s the percentage of emails your recipients open, and although this isn’t as accurate as it used to be, generally, you’ll want this rate above 50% and need to keep an eye out for declines as an early signal of deliverability issues. 

7. Unsubscribe and Double Opt-in Provisions

Not all your contacts may be interested in your emails, and they might prefer a way out to stop receiving your emails. 

Including an option to unsubscribe gives your prospects a chance to stop receiving your emails. 

If you don’t do so, uninterested contacts might be more likely to report your emails as spam to stop receiving them and dent your deliverability.

Likewise, for prospects who’ve subscribed to your email list, adding another opt-in link to confirm their subscription ensures that they’re genuinely interested and not likely to flag your emails. (this is called double opt-in). 

Now, let’s look at some best practices that can help boost your email deliverability efforts.

10 Actionable Tips to Boost Your Email Deliverability

Here are 10 handy tips to enhance your outreach campaigns to improve deliverability:

1. Set Up Appropriate Authentication Protocols

Authenticated emails let ESPs know that your messages are legitimate and originate from your end. 

If your contacts receive emails from a domain different from the actual sending domain, they won’t trust the emails and might mark them as spam.

Setting up the SPF and DKIM authentication records prevents forgery and adds encryption keys to validate your emails. 

With the DMARC protocol, you can ensure contacts that your emails are protected with SPF and DKIM, enhancing your deliverability.

2. Sending through Email Client Instead of a 3rd party SMTP 

Although third-party SMTPs offer scalability and convenience, they are often linked to sales and marketing emails. 

This makes them trigger spam filters as they can send bulk emails in a short period of time and are considered risky.

For best email deliverability, go for IP addresses associated with your paid client email, like G Suite or Outlook email accounts. 

These services are typically used for professional communication and are generally considered trustworthy and lower risk by mailbox providers - ensuring a successful email delivery to your recipients' inboxes.

3. Avoid Spammy Language and Content

Spam filters have evolved to look beyond spammy words and detect excessively salesly and generic-sounding language in your emails. 

If your email subject line or content makes false promises or sets sky-high expectations, the message will wind up in spam. 

Your emails can also be more likely to end up in the junk folder if they contain too many images, large attachments, or video files. 

Keep your email content brief and focused on the prospect to improve engagement and deliverability.

4. Develop a Hyper-focused Prospect List  

While you may be tempted to mass email anyone in a specific sector/job, reaching out to prospects based on their interests is better. 

A good strategy is to segment your contact list based on specific data points like:

  • The content your prospects engaged with on Twitter or LinkedIn 
  • Any change in your prospect’s current tech stack
  • The reviews left by your prospect’s company’s employees on Glassdoor, etc., and so on

Sending emails tailored to your contacts’ intent and issues keeps them engaged and more likely to engage, raising your deliverability rate.

5. Send Personalized Email Campaigns and Follow-Ups

Segmenting your email list and sending prospects content suited to their needs gets their attention, but personalized campaigns keep them interested. 

Customizing your outreach emails and follow-ups based on data you have about your prospects increases your emails’ open and click-through rates.

This improves your inbox placement and email deliverability in the long term. 

6. Maintain a Clean and Healthy Prospect List

To enhance your long-term email deliverability, developing a process where you avoid reaching out to risky contacts is essential. If you don’t have a final line of defence to avoid emails sending to invalid contacts, spam traps, low engagement emails or known spam reporters you’ll see bounce rates above 2.8% regularly. 

A high bounce rate reflects poorly on your overall inbox placement and deliverability. Use a solution like an email Safety Net, which integrates to your sending platform to help mitigate these risks.  

7. Test Your Outbound Emails Before Sending Them

Test your outreach campaigns by sending them to yourself to check how they look in your prospect’s inbox. 

Besides, you must ensure your emails are legible on mobile devices, and testing them beforehand helps you fix any formatting issues, display errors, and more.

You can also preview your messages on an email deliverability tool like Allegrow and resolve any problems with their design and template.

8. Encrypt Your Emails with TLS

TLS or Transport Layer Security is a type of email encryption that safeguards your content from being read by anyone other than the intended receivers. 

Email encryption via TLS is also a type of authentication. It ensures that no undesired third party can access or tamper with your email communications. 

9. Use a Dedicated Subdomain For High Volume of Emails

By using a subdomain for sending high volume of emails, you isolate your email marketing activities from your primary domain. This separation helps protect your primary domain's reputation. 


If a deliverability issue comes up with your email marketing campaigns, they are less likely to affect your primary domain's email deliverability. You can also customize authentication settings for your subdomains without affecting the primary domain.

Subdomains also help you analyze email deliverability issues easily, determine which emails are causing the deliverability issue and sort it out before it further damages your domain reputation. 

This proactive approach ensures that your emails consistently reach the inbox and don't end up in spam folders, which can negatively impact engagement rates.  

10. Craft Engaging and Relevant Content 

While authentication, validation, and other strategies can help you reach your recipient’s primary inbox, spammy content might turn them off right away.

Once you reach your prospect, it’s crucial to provide relevant content to them or address their pain points. Such emails will hold your prospects' attention, making them open to a discussion and ensuring you’re follow-ups don’t come across as inpatient.

Let’s next look at some emerging industry trends you should keep an eye on to boost your email deliverability.

5 Emerging Email Deliverability Industry Trends 

Here are the five upcoming industry trends to watch out for in email deliverability: 

1. Avoiding Risky Contacts

While bulk emailing all prospects was a trend of the past, it’s more common now to avoid unengaged contacts. Unengaged contacts have stopped interacting with your emails mostly because they’ve lost interest or your messages aren’t relevant to them anymore.

In either case, such contacts are also likely to report you for spam to stop receiving your emails. 

2. Warming Up the Domain

When using a new domain to launch a marketing campaign, marketers warm it up before cranking up their outbound emails. Warming up entails starting sending on a new subdomain to the most engaged and highest quality segments of contacts you can source.

Sending out bulk emails from a new domain can set off a spam filter, while warming up the domain before emailing campaigns makes you more trustworthy and authentic to the recipient internet service provider.

Warm-up providers also provide interactions, like replies, to emails that get automatically sent from your inboxes to help support this process. 

3. Throttling Sending 

Another trend complementing domain warm up is throttling sending. Most ESPs have certain thresholds for increases in sending activity on mailboxes they’ll see as abnormal and high risk. 

Since providers won’t share clear guidelines on what they consider risky, marketers throttle the number of their outbound emails. They’ll start with a small number to warm up their domain and steadily increase their outbound emails to an acceptable, optimum range. 

4. Hyper-Personalized Content

Mass emailing all your prospects the same generic email is just white noise that recipients are likely to ignore or even mark as spam. 

Your emails should be customized to address their specific pain points and give context on why you expect your subject matter is top of mind for them.

You can also engage them by enquiring about any new milestone they posted on social media or using any behavioral information you’ve collected about them.

For instance, instead of saying – “I expect hiring sales reps is top of mind for you. Would it be helpful to provide them with a dedicated external mentor?” You could say “Saw you brought Joe onboard - Congrats {FirstName}! Curious if you’ve ever considered an external coach for new reps?” 

5. Disengagement Triggers

A great way to engage prospects is to build trust and nurture a human connection with them. 

However, not all your prospects may be keen to hear from you at all times. It’s vital to segment your contact list and identify disengagement triggers. If open and click rates decline, or you stop receiving feedback from a previously interested prospect, it may be time to take some prospects off your contact list. 

While all the above tips and strategies can help level up your email deliverability, a handy tool like Allegrow can truly transform your efforts.


Let’s find out.

Improve Your Email Deliverability with Allegrow

Allegrow is a tool that helps enhance your email deliverability, improve your sender reputation, and boost your inbox placement. It helps you manage and mitigate the risk of landing in spam folders when you’re running outbound email campaigns. 

With Allegrow, you can:

  • Connect to major B2B email providers like Google Workspace, Office 365 and custom on-premise email servers to gather spam rate data.
  • Identify risky contacts in your outgoing emails to avoid recipient ESP’s spam trap. This helps you avoid invalid contacts and stay away from prospects who are likely to report or ignore you.

  • Create a unique knowledge base regarding your industry and unique value preposition.

  • Use A/B testing and AI content drafting to choose the best email content to bypass spam filters and reach your prospect’s primary email folder.

  • Compare the real-time spam rates of users on your leaderboard and address issues without affecting your sender reputation.

  • Deploy Allegrow’s analyses of thousands of spam folders to obtain valuable insights on the type of content being reported by spam filters.

  • Show prospects your emails' value and engagement potential through Allegrow’s interactions.

  • Track your inbox placement reliably with Allegrow’s trustworthy network of 2,500 business email addresses.

  • Get regular updates on your sender reputation and check how frequently your messages end up in recipients spam box.

  • Conduct hourly checks to ensure your SPF, DKIM, and DMARC protocols are working as they should. 

  • Integrate directly with sales engagement platforms like, Salesloft, and CloseCRM.

Boost Your Email Deliverability with Allegrow

Email deliverability is essential for the success of your email campaign. However, trying to improve your deliverability manually without any external help can be cumbersome and inefficient.

With a tool like Allegrow, you can identify problem areas and tackle them effectively, all via one platform.

Get a free audit of your email deliverability today.