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How to improve email deliverability?

10 min read

Connecting with your users is essential for any business, and email remains one of the most effective channels for direct communication. Unlike social media platforms, which may come and go, email has stood the test of time since the inception of the Internet and continues to be a constant in our digital lives. This blog aims to enhance your ability to reach your audience by offering actionable insights on improving email deliverability. We’ve also recently tackled this critical topic in our LiveStream Coding session with Nylas, providing a deeper dive into the strategies for optimizing your email campaigns:

What is email deliverability?

Email Deliverability is the probability that an email sent will successfully arrive in the recipient’s inbox rather than being marked as spam or lost in transit. This is often expressed as a percentage, indicating the ratio of successfully delivered emails to the total sent. The metric is influenced by various factors, including sender reputation, email content, and user engagement.

Email deliverability factors

Understanding the factors that impact email deliverability is crucial for anyone looking to optimize their email campaigns. These factors act as the building blocks that dictate whether your email reaches the inbox, lands in the spam folder, or gets lost in transit. From the reputation of the IP address sending the email to the quality of the contact list and the content within the email itself, each aspect plays a significant role in determining your email’s final destination. In the following sections, we will delve into these key factors to provide a comprehensive understanding of what influences email deliverability.

IP reputation

IP Reputation is a crucial factor that email service providers consider when determining whether your email should reach the recipient’s inbox or be filtered into spam. This reputation score is built over time based on the behavior associated with your IP address. For example, sending high volumes of emails or receiving numerous spam complaints can negatively impact your IP reputation score. Internet Service Providers (ISPs) use this score to gauge the trustworthiness of your emails. A high score increases your chances of bypassing spam filters, while a low score could result in your emails being blocked or sent to the spam folder. Maintaining a strong IP reputation is vital for optimizing email deliverability.

See below how Nylas can help to improve IP reputation.

Contact list quality

Contact List Quality is another pivotal factor that directly influences your email deliverability rates. A high-quality contact list consists of verified, engaged recipients who have opted-in to receive your communications. Sending emails to low-quality addresses like spam traps or inactive accounts can severely impact your email deliverability. For instance, hitting a spam trap—a fake email address set up by ISPs to catch spammers—can significantly lower your reputation score. Thus, regular list cleaning to remove inactive or fraudulent addresses, along with implementing double opt-in procedures, can go a long way in maintaining a high-quality contact list and, consequently, improving your email deliverability.

See below how Nylas can help to improve the contact list quality.

Email schedule

Email Schedule plays an instrumental role in affecting your email deliverability. Sending emails in large volumes, either all at once or over a short period, can raise red flags with email providers, leading to reduced deliverability rates. Strategic timing and pacing of your email campaigns can improve the likelihood of your emails reaching the intended inboxes. Spacing out your emails and adhering to a consistent sending schedule not only aligns with best practices but also helps in maintaining a positive IP reputation. Therefore, optimizing your email schedule is a key step in ensuring that your emails effectively reach your users.

See below how Nylas can help to improve the email schedule.

Email analytics

Email Analytics serve as vital indicators for understanding how your emails are received and interacted with, ultimately affecting your email deliverability. Important metrics to consider include:

  • Open Rates: Monitoring how often your emails are opened can provide insights into the relevance and effectiveness of your email subject lines and content.
  • Email Bounce Rate: A high bounce rate is often a red flag for email providers, as it could signify that your contact list is outdated or of poor quality.
  • Time Spent Reading: The duration for which a recipient reads your email can be a valuable engagement metric, and it can influence how email providers view your content.
  • Click-Through Rates: This measures how often people who open your email actually click on any embedded links, and it’s another strong indicator of the email’s relevance and quality.

By regularly tracking these metrics, you can make informed decisions to tweak your email campaigns, thereby improving their effectiveness and your overall email deliverability.

See below how Nylas can help to improve the email analytics indicators.

Email content

Email Content is a pivotal element that directly impacts your email deliverability. The quality and relevance of the content you send can either engage your recipients or turn them away. Personalization is key; tailoring your emails to the individual recipient enhances the user experience and increases engagement metrics like open and click-through rates.

  • Personalization: Customizing your emails to include the recipient’s name or references to past interactions can make the content more relevant and engaging.
  • Relevance: Sending timely and contextually appropriate content will likely resonate more with your recipients, thereby positively affecting your email metrics.

By focusing on creating high-quality, personalized content, you not only improve user engagement but also positively influence email deliverability rates.

Content is important when it comes to email. Personalizing your email is important to ensure it is well received by your users and is relevant to them. This will impact your email metrics and also impact email deliverability.

See below how Nylas can help to improve the email content.

How to check email deliverability

Checking Email Deliverability is a crucial step for identifying potential issues that could be affecting the reach and impact of your email campaigns. Various online tools are available to help you assess where you may be falling short:

  • ISnotSpam: This tool conducts multiple tests on your email content and settings, providing you with a pass/fail result to quickly identify areas of improvement.
  • MXToolbox: This resource checks if your IP address is blacklisted and offers an Email Deliverability tool to provide a more comprehensive analysis.

Beyond utilizing these tools, you should also monitor the following metrics for any sudden changes that could indicate deliverability issues:

  • Email Bounce Rate: A high rate can signify that your emails are not reaching the intended recipients, warranting immediate investigation.
  • Email Open Rate: A sudden drop in open rates could suggest that your emails are being marked as spam or not engaging the recipients effectively.

Regularly checking your email deliverability using these tools and metrics can provide you with valuable insights, helping you to proactively address issues before they escalate.

How to improve email deliverability

Improving Email Deliverability is essential for maximizing the effectiveness of your email campaigns. Using tools like Nylas, you can take targeted actions to enhance various elements that contribute to deliverability. Here are some ways to achieve this:

1. Improve IP reputation

Use Nylas Email API to send emails on the user’s behalf, thereby leveraging their IP reputation as an alternative to using a generic transactional email service provider.

Here is a code sample of sending an email on your user’s behalf:

# {{url}} is the Nylas API endpoint
curl --location -g --request POST '{{url}}/send' \\
--header 'Content-Type: application/json' \\
# {{access_token}} is the user's access token
--header 'Authorization: Bearer {{access_token}}' \\
--data-raw '{
    "body" : "Thanks for visiting, here are your order details.",
    "subject": "We're processing your order W12408221",
    "to": [
            "name": "{{name}}",
            "email": "{{exchange_email}}"

2. Improve contact list quality

Using the Nylas Email API, you can follow up with re-confirmation or double opt-in emails to avoid possible spam traps that will impact your email deliverability. It’s also worth considering completing fraudulent checks for users before sending the email, such as scanning their IP or email against known lists of bad actors. You can also add your application email to your user’s contact list to be considered a safe sender using the Nylas Contact API.

Here is an code sample of adding your application to your user’s contacts:

# {{url}} is the Nylas API endpoint
curl --location -g --request POST '{{url}}/contacts' \\
--header 'Content-Type: application/json' \\
# {{access_token}} is the user's access token
--header 'Authorization: Bearer {{access_token}}' \\
--data-raw '{
  "emails": [{
  	"type": "Nylas",
  	"email": "devrel@nylas.com"

3. Improve email schedule

Using the Nylas Email API, you can decide when to send the emails. You can call our Email API at your own preferred time/day to improve email deliverability.

Also, you can decide how frequently to send out multiple emails to many recipients by spacing them out and calling the Email API at a certain frequency, like every 30s or sending an email once a minute.

4. Improve email analytics

Using our Nylas Email API and with a connected user account, you can check and learn more about email engagement. So learning about if the email is unread, or starred is possible using the Nylas Email API.

Another area to consider is tracking if emails are being delivered to the recipient. So if you start receiving error codes using the Nylas Email API, this may be a sign that emails are bouncing and you should consider pausing sending emails for a period of time before restarting.

Here is a code sample of retrieving a message and a sample response that contains properties starred and unread:

# {{url}} is the Nylas API endpoint
curl --location --request GET '{{url}}' \\
# {{access_token}} is the user's access token
--header 'Authorization: Bearer {{access_token}}'

# API Response
        "account_id": "{{account_id}}",
        "bcc": [],
        "body": "Order details...",
        "cc": [],
        "date": 1673852731,
        "events": [],
        "files": [],
        "from": [
                "email": "{{email}",
                "name": "{{name}"
        "id": "{{message_id}}",
        "labels": [
                "display_name": "Category Updates",
                "id": "a0sdwue0287lhsk9itxz2q377",
                "name": "updates"
                "display_name": "Inbox",
                "id": "49eh9pixzuj18pbe78lntkbf4",
                "name": "inbox"
        "object": "message",
        "starred": false,
        "subject": "Insights Digest - Week of Jan 9 for Nylas",
        "to": [
                "email": "devrel@nylas.com",
                "name": "Nylas"
        "unread": true

5. Improve email content

When sending an email, try to personalize the content as much as possible. Mail merge is where you combine data with information such as a person’s name and previous transactions with an email to create a personalized message. Using mail merge and the Nylas Email API you can send personalized messages to users that get more engagement and improve your email deliverability.

How to ensure email deliverability with Nylas?

Ensuring email deliverability is a continuous process that involves careful consideration of multiple factors. Leveraging the capabilities of Nylas Email API, you can take specific actions to fortify the deliverability of your email campaigns:

  • Maintain a Solid IP Reputation: Use your users’ email addresses to send emails, thereby capitalizing on their already established IP reputation. This enhances the trustworthiness of your outgoing emails.
  • Quality of Contact List: Ensure that your list is regularly cleaned and updated. Employ double opt-in procedures and scan for potential bad actors to maintain a high-quality contact list, which in turn boosts deliverability.
  • Scheduled Sending: Utilize Nylas to send emails at specific times of the day and at reasonable frequencies, avoiding the risk of being flagged as spam due to irregular sending patterns.
  • Track Email Engagement: Keep an eye on crucial metrics like email open rates and send errors. Sudden changes can be indicative of underlying deliverability issues.
  • Personalize Content: Use mail merge features in Nylas to personalize your emails. Customized, relevant content is more likely to engage recipients, thereby improving deliverability.

By integrating these best practices with the advanced features offered by Nylas, you can ensure a more reliable and effective email deliverability strategy.

Learn more by visiting the Nylas Email API overview. Sign up here if you need to create a Nylas account for free!

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