Understanding Email Domains, Subdomains and Aliases

The industry best practice is to send marketing emails from a subdomain, rather than the root domain. How does this help your email marketing? To better understand how this can affect your deliverability, you first need to understand what a domain and subdomain is.


What is a domain?

A domain is a human-friendly way of identifying a website. This is also referred to as the parent domain or root domain. It was introduced to make IP, or Internet Protocol, addresses more accessible.


An IP address is a string of numbers that are assigned to every computer but memorizing is a lot harder than Cognism.com.


In basic terms, if the website is your house, the domain would be the physical address, the exact location of your website.


A domain name typically has two parts: top-level domain (TLD) and second-level domain (SLD) and these are vital to the identity of any brand, company, legal entity, or individual wanting to position itself on the Internet.

  • Top-level domain (TLD) is the domain extension or what comes after the dot.

    • The most common extension .com makes up for 46.5% of all global websites, but that still leaves plenty of room for other domain extensions like .org, .net, .edu etc.

    • Some websites use nation explicit domain names which end with nation code expansion like .uk for the United Kingdom, .de for Germany, etc.

  • Second-level domain (SLD) is the section before the dot, or the unique part of the domain name.

Similarly, the domain name is used for sending emails. It is the unique name you see in email addresses after the @ sign.


When sending personal emails, you use the domain name of Internet service providers or webmail providers (Outlook, Gmail, Yahoo, etc.). But employees of a company send their emails from a customized domain name that reflects the brand, and their email addresses usually follow a certain pattern (firstname.lastname@yourbrand.com).



Let’s suppose you are using the same domain as your website for your marketing and sales mailings. Imagine for a moment that sending from this marketing address meets bad deliverability and you end up blacklisted or banned by the main Webmails or ISP. Your domain name would be put in danger and none of your business emails would be delivered to the inbox! This is where subdomains come into play.



What is a subdomain?


A subdomain or a third-level domain is the child of the parent domain. It goes directly before the SLD and is most commonly used to separate sections of a website or departments in a company for a specific function.


For example, you can visit cognism.com to view the services offered by our company. Or you can visit app.cognism.com to access our prospecting tool. So even though the URL changes slightly, you are still on Cognism’s website, under Cognism’s domain.


Without getting too technical, the most important thing to remember here is that subdomains have a different reputation than their root domains. They are essential for building a strong, stable sending reputation and when it comes to email marketing, reputation is king. By using subdomains, you are ensuring that if something goes wrong, the parent domain is not affected and all other emails sent by your brand will go through to the intended recipients, limiting the business impact of the bad deliverability significantly.


Note: The name of your subdomain doesn’t matter in terms of email reputation, though it helps to be clear as possible to avoid confusion among users.



What is an email alias?


As we mentioned above, each mailbox or email address has one main “name” that goes before the @ symbol. An email alias is basically an additional nickname that is added to your primary email mailbox and the alias itself has no inbox and no login. It only exists to forward all incoming messages to your primary email account. It also uses the same account settings and contacts as the account you consider primary.


One important thing to remember is that aliases do not protect the health of your domain. They are just a ‘front’ for your main inbox so if you are using your business root domain for sending and meet bad deliverability the entire domain will suffer the negative consequences.


When are email aliases useful:

  • When someone fulfills multiple roles in a company: instead of switching between several inboxes, all emails are forwarded to the primary inbox allowing the user to easily track all inbound messages.

  • Temporary address for online use: for instance, a marketing campaign or posting a job opening. Once the purpose of the alias has been fulfilled you can easily delete it and immediately stop receiving all unwanted emails to that address.

  • Employee no longer at company: let’s say jsmith@yourbrand.com has left the company and you no longer need that mailbox but you do want to get future emails sent to that email address. You can simply add jsmith as an alias to your own mailbox and any email sent to them will arrive at your primary inbox.

Note: There are also domain aliases. These are similar to email aliases, but instead of the main “name” before the @ symbol, a domain alias is the part after the @ symbol.


This is useful when you want to merge a few company mailboxes into one service.

For example, your main email address is johndoe@yourbrand.com. But you have another company called: Branding.


You can create a domain alias johndoe@branding.com, where the domain is @branding.com.
Now when emails go to either one of these emails, they will arrive to the same main or primary mailbox.

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