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IMPORTANT: Glossary of Terms on Email Deliverability

Hey guys, Pepe here the Co-Founder of Mailyser. During my time in email, I have dedicated special effort to understand what moves the needle when it comes to email deliverability. This aspect is key in determining the effectiveness of your email campaigns and is often overlooked by many. I have put a glossary of terms below to inform the uninitiated and refresh the memory of the wise!


DMARC (Domain-based Message Authentication, Reporting, and Conformance)

DMARC is a protocol that helps protect email domains against unauthorized use, such as email spoofing and phishing attacks. It allows domain owners to specify that their emails are protected by SPF and/or DKIM and provides instructions for handling emails that fail authentication checks.


SPF (Sender Policy Framework)

SPF is a security technique used to prevent sender address forgery. It enables the domain owner to declare which mail servers are permitted to send email on behalf of the domain. This verification process helps to ensure that emails are sent from authorized servers, thereby reducing spam.



Email deliverability refers to the likelihood of an email being successfully delivered to the recipient's inbox, bypassing spam filters. Factors influencing deliverability include the sender's reputation, recipient engagement, and the content of the email.



The inbox is the desired destination for all email marketers, indicating that the email has successfully bypassed spam filters and has been delivered to the recipient's primary mail folder.


Promotions Folder

The Promotions folder is a classification within email services like Gmail, designed to segregate marketing and promotional emails from primary correspondence. This helps users manage their inbox by categorizing emails based on content.


Open Rate

The open rate is a metric that measures the percentage of email recipients who open a given email. It is an essential indicator of how engaging an email subject line is to the audience.


Click Rate

The click rate measures the percentage of recipients who click on one or more links contained within an email. It is a critical metric for assessing the effectiveness of the email content and call-to-action.


IP Address

The IP address is a unique identifier for the sender's internet connection, critical for establishing the sender's reputation. Email services evaluate the IP address's history to determine the legitimacy of the sender.


Dedicated IP vs. Shared IP

A dedicated IP address is assigned exclusively to a single sender, allowing full control over the sender's reputation. In contrast, a shared IP address is used by multiple senders, meaning the reputation is influenced by the collective behavior of all users.


IP Reputation

The IP reputation is an assessment of the trustworthiness of an IP address, based on its email sending behavior. A positive reputation enhances deliverability, while a negative reputation may lead to emails being blocked or marked as spam.


From/Sending Address

The from or sending address is the email address displayed to recipients. It is crucial for establishing identity and trust with the audience.



SPAM refers to unsolicited, often irrelevant emails, sent in bulk to a large number of recipients. High levels of spam can damage a sender's reputation and deliverability.



The unsubscribe option is a legally required feature that allows recipients to opt-out of receiving future emails. This fosters a respectful relationship by giving recipients control over their inbox.


Feedback Loop

A feedback loop is a mechanism through which senders can receive notifications when recipients mark their emails as spam. This feedback is valuable for improving email practices and maintaining a healthy sender reputation.


Seed List

A seed list is a carefully selected list of email addresses used to evaluate the deliverability and appearance of emails across different email providers before launching a broader email campaign.



The content of an email includes all textual, visual, and interactive elements. Effective content is engaging, relevant, and tailored to the recipient's interests and needs, driving the desired action.




Familiarity with these terms provides a foundational understanding of email deliverability, a critical component of successful email marketing strategies. At Mailyser, our goal is to empower marketers to achieve optimal deliverability, ensuring that their messages not only reach the inbox but also engage and convert their target audience.

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