Deliverability: Overview

Jan 30, 2026
Knowledge

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This article explains the basics of email deliverability, authentication, and sender reputation

	In This Article
	Video Overview Delivery vs. Deliverability Authentication Sender Reputation Additional Resources

Delivery and deliverability are not the same thing. Delivery simply means that a mailing is accepted by the receiving mail server. If a mailing is rejected by the receiving mail server, that is called a bounce. If a mailing is not rejected or bounced, it typically ends up in either the subscriber's inbox or their spam folder.

Ⓘ	Info
	A mail server is a machine and software that sends and receives emails.

Deliverability means that a mailing reaches your subscribers' inbox or folder of choice. You can improve your deliverability through a combination of best practices and technical settings, which we will go over below.

More delivery and bounce resources

Authentication

Email authentication is a key step in securing your identity online. Similar to having a valid passport when traveling overseas, email authentication proves to receiving mail servers that you own the domain you're sending from. Email authentication has always been best practice, however, many major inbox providers now require it, so not setting it up can have a serious impact on both your delivery and your deliverability.

✎	Note
	Your domain is the part of your email address after the @ symbol, which is usually the same as your website address. You cannot authenticate a domain that you do not own, so if you don't own a domain, you'll need to purchase one.

There are three methods that you can use to identify and authenticate yourself as the legitimate sender for your domain:

DomainKeys Identified Mail (DKIM)
Domain-based Message Authentication, Reporting, and Conformance (DMARC)
Sender Policy Framework (SPF)

In Emma, both DKIM and DMARC are required. SPF is optional, but encouraged.

DKIM

DKIM is directly tied to your sending domain and functions as a digital signature for your mailings to prove that they haven't been tampered with while in transit. Senders must set up DKIM authentication with Emma for their sending domain, as this helps receiving servers identify legitimate mailings.

DMARC

A DMARC policy tells mail servers how to treat emails that fail authentication, which will happen if you do not set up DKIM. Based on your DMARC policy, receiving servers will either do nothing (p=none), put unauthenticated emails in the spam folder (p=quarantine), or bounce unauthenticated emails (p=reject). Only the domain owner can set up DMARC and DKIM, so together they help inbox providers correctly identify your legitimate emails.

SPF

SPF checks that the mail server sending the email is authorized by the domain owner. Most email service providers (ESP), including Emma, use their own domain for SPF checks. Because of this, it's a good idea to include Emma's domain in your SPF record, to show a relationship between you and your ESP, but it's not required.

More email authentication resources

Sender Reputation

While email authentication is vital, it's not enough to guarantee successful delivery on its own. Receiving servers also consider sender reputation when deciding how to handle incoming emails.

Your sender reputation is built over time based on your sending practices and subscriber engagement. Maintaining a positive sender reputation shows that you're a trustworthy sender, which improves the likelihood of your emails reaching recipients' inboxes.

Sender reputation is shaped by your actions in four key areas:

Maintaining fully permission-based email lists
Regularly removing inactive or unresponsive contacts
Monitoring and analyzing engagement metrics
Sending relevant and engaging content

Inbox providers monitor spam complaint rates and so do we. Our complaint threshold is .02% - if a campaign exceeds that threshold, our Compliance team will reach out to help you get back on track. Luckily, the key to minimizing spam complaints is to adopt the same best practices that will protect your sender reputation.

Ⓘ	Info
	Spam complaint rate is calculated by taking the number of emails marked as spam by recipients, divided by the total number of emails delivered.

While reputation is not a tangible measurement that inbox providers share with ESPs, you can use your open and click rates to infer your reputation. If they are improving, then your reputation is likely improving.

Permission-Based Lists

Using fully permission-based email lists is one of the most important factors for building and maintaining a strong sender reputation. Sending unsolicited emails can seriously harm your sender reputation.

Whenever possible, send a welcome email to confirm new contacts' subscription and outline what kind of content they can expect to receive from you. Sending to contacts who have not agreed to receive your emails can lead to low open rates and high spam complaints, which can harm your reputation and deliverability.

More permission-based list resources

Inactive Contacts

Regular maintenance of your email list is essential for ensuring that it remains healthy and engaged. It's important to ensure that your lists only include subscribers who are engaging with your mailings on a regular basis, since their engagement directly impacts your reputation.

Review your database periodically to identify inactive contacts. Consider sending a re-engagement campaign to contacts who haven't engaged in the past six months, to encourage them to reconnect with your content. If they remain unresponsive after 12 months, it's better to remove them from your list. While it may seem counterintuitive to reduce your audience size, a targeted, engaged list is far more beneficial to your email performance and reputation than sending to a larger list with more unresponsive contacts.

More list maintenance resources

Monitoring Engagement

Response metrics are a valuable tool for assessing the success of your emails and a way to measure your engagement with your audience. Key metrics like open rates, click rates, and bounce rates provide insights into how your audience interacts with your content.

Use these insights to refine your email strategies. For example, you can create audience segments based on engagement levels or test different subject lines, sending times, or content types to optimize performance. Regular engagement monitoring not only helps you improve your campaigns, but also signals to receiving servers that your emails are valued by recipients.

More engagement and response resources

Relevant Content

Sending relevant, personalized content is critical to keeping your audience engaged and maintaining a strong sender reputation. Your contacts have signed up with specific expectations, so it's essential to meet or exceed them by tailoring your emails to their interests and needs

Use segmentation and personalization to create emails that feel meaningful to your audience. Over time, establish benchmarks for your open and click rates and use these metrics to experiment and optimize your content. Thoughtful, targeted content not only improves engagement, but also contributes to a better reputation with ISPs and inbox providers, ensuring your build and maintain good deliverability in the future.

More content and personalization resources

Additional Resources

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Deliverability: Overview

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deliverability-overview