Vladislav Podolyako
Jan 14, 2021
Reading duration

Email deliverability is a complex subject. 

First, it takes a while before you can say with confidence that all your emails are completely deliverable and your outreach is flowing as intended. A good reputation isn’t built in a day, after all.

Second, there is no metric called “email deliverability.” Instead, several KPIs point out the state of your email deliverability and many technical factors that influence it. So, in order to make sure your emails are properly delivered, you must be able to look behind the curtains of email outreach, see how the gears turn and find out what makes it tick. 

Sure, it can be a time-consuming process, but you don’t have to start with the hard stuff. Within this blog post, you can explore basic email deliverability terms. From our experience, almost every email user comes across one or two of those in the middle of their email outreach. In the majority of cases, they aren’t ready for that encounter, wasting weeks on trying to edit their SPF record or figure out what their mailbox has to do with MTA reputation. So, the more you know before you get started, the less of a challenge your email deliverability will be. 

What will this knowledge give you?

  • You’ll know how to start your email deliverability test right.
  • You’ll be able to map out the steps for improving your email security and building safe communication between you and your recipients.
  • In case you hire a team to take care of your outreach, you will be able to quickly navigate your mailbox engineers through the issues that impact your performance.
  • You’ll gain a better understanding of how electronic mail transmission works and how users are identified.

The Ultimate List of Email Deliverability Definitions

Sender Reputation

Sender reputation is the quality of your email campaigns based on their scale, frequency, and interactions with the recipients. Mailbox providers study sender reputation carefully before letting incoming emails land in users’ inboxes. Just like email deliverability, sender reputation cannot be measured by a single metric, so you should pay attention to its foundational components — IP reputation and domain reputation. 

IP Reputation

IP reputation is a constantly updating chronicle of activities that have been registered on your IP address. You start building your IP reputation as soon as you get an email address and start sending messages. Actions, such as sending to invalid email addresses, exceeding the daily message limit, or sending emails inconsistently, negatively impact IP reputation, while building a schedule, sending small batches of emails, and using clean email lists improves your reputation and increases the receiving servers’ trust. 

Domain Reputation

Also called “domain health,” domain reputation reflects mailbox providers’ stance towards your email domain and shows your status as a sender. Suspicious or malevolent activities (spam triggers in the body text, lack of proper technical settings, misleading subject lines) mark the domain as corrupted or compromised, prompting receiving mail servers to blacklist it, isolating it from the recipients. To keep your domain health high, you must use an email spam checker, implement anti-spoofing measures, and make sure that receiving servers can easily authenticate your identity. 

MTA Reputation

Many users become acquainted with the MTA (Message Transfer Agent) reputation after trying to send a message and receiving a 554 error notification saying, “Your access to this mail system has been rejected due to the sending MTA’s poor reputation.” It means that they sent an email from an IP address that was blacklisted by the receiving server. 


ISP or Internet Service Provider is a company or an organization that provides the means and technology for accessing the internet. An ISP can be an access provider or a  mailbox provider, i.e., a company that specializes in services that revolve around email domain hosting and mailbox storage.


ESP or Email Service Provider is an organization that offers a broad set of email marketing services such as template crafting, template testing, send engines, spam testing, etc. 


A blacklist is a list created by an ISP to identify spammy or suspicious domains and IP addresses. After being blacklisted, a domain or an IP is banned from sending emails as a safety measure.    


A direct opposite of a blacklist, a whitelist is a list featuring identified users and business entities that have proved their credibility and are granted instant access to a mail system. In terms of email outreach, the emails sent from a whitelisted domain skip filter checks and go straight to the recipients’ inboxes. 


To put it simply, the Domain Name System is a virtual phone book that identifies IP addresses as well as the domains they belong to. The DNS includes several designated authoritative name servers for each domain (.org, .com, .eu). Those servers deal with assigning and mapping domain names to Internet resources, ensuring a fault-tolerant performance. 


Spoofing is a phishing tactic in which a phisher or a phishing program forges data and assumes a trusted sender's identity to get access to private information. Email spoofing involves using email addresses that resemble the ones that belong to credible organizations (corporations, international associations, etc,). Thus, users are tricked into opening an email or changing their payment details. 

SPF Record

An SPF record or a Sender Policy Framework is a txt. a record that is published in the DNS records for your domain. Introduced as a measure against spoofing and other sender data forgery, this record features all domain names and IP addresses that allow for sending messages on your behalf. An SPF record can be added and edited by the user via special kits provided by a mailbox provider. 


The DMARC (Domain-Based Message Authentication, Reporting, and Conformance) protocol is another anti-spoofing and anti-phishing measure that provides receiving servers with instructions authenticating incoming messages. DMARC is firmly based on the information exchange, allowing senders to publish DMARC records that request information on spam and phishing attacks from the receiving domains. 


A DomainKeys Identified Mail or DKIM is an encrypted signature featured in the headline of incoming emails. Only visible to the receiving servers, DKIM certifies that the message is sent by an identified user and hasn’t tampered with it had been sent.   


A CNAME (Canonical Name) record is a DNS resource record that maps the connection between subdomains, domain aliases, and a canonical domain name. CNAME is mostly used for managing multiple services from a single IP address, allowing users to bind addresses and names to the canonical domain name. 


Short for Simple Mail Transfer Protocol, SMTP manages the transmission of electronic messages within the TCP/IP network. SMTP is the most widespread communication protocol used by a large variety of message transfer agents and mail servers, so nearly all anti-spoofing and email security protocols are adapted to it. 


Fix your email deliverability issues

We hope this short guide will help you find your way through all the odd terms and abbreviations as you put your outreach campaign together. However, once you get started, you may encounter some issues associated with the terminology mentioned above. This is why we suggest getting equipped with a proper analytics and monitoring service. Folderly provides a wide set of tools and features to help you make sense of your deliverability and nip all the issues in the bud while keeping your budget intact.

Vladislav Podolyako
Vladislav Podolyako
Founder & CEO
Vlad’s decades of entrepreneurial wisdom and business building experience have allowed him to successfully mentor a diverse group of business owners, entrepreneurs in growing their companies. A recognized expert in the areas of transforming organizational culture and leadership development, B2B Sales, Marketing, spent more than 10 years building technology products, with a background in communication networks and electronic device engineering.