What about the third-order domain?

[suchona.kani.z]

Will sending marketing messages from a subdomain help you protect the reputation of your primary domain? Until recently, the prevailing opinion was that it would. However, we have learned the opposite. Let's now take a closer look at the importance of a 3rd-level domain.

What is a 3rd order domain?
First, a short summary. Domains are divided into three levels – first, second, and third order.

The top-level domain is the very last part of your email address . It is most likely CZ (.cz) or COM (.com).
The second-level domain is the main part of the address and in the vast majority of cases contains the company name (@company.cz).
A third-level domain, or subdomain, is an extension of an address (or domain name) by another word. For example, @obchod.firma.cz, @novinky.firma.com.
explanation of first, second and third order domains
This is what third-order domains look like. We commend the Luxor Bookstore for its unusual idea.
Why send from a subdomain?
The main reason was to ensure that in the event of any ios database problems, the reputation of the main domain from which you send transactional messages that are important to customers (order confirmation, payment details, preparation of the shipment for pickup, etc.) would not be damaged.

It seems logical - these transactional emails usually come directly from the e-shop solution under the main domain (@company.com), while newsletters come from the e-mailing tool under the subdomain (@news.company.com). So if your marketing mailing happens to be disliked by recipients or spam filters and the newsletters start falling into spam, the transactional messages will be "out of date" .

How is it really?
Nowadays, you won't find any sources that say it should work like this . On the contrary, for example, in an article from ActiveCampaign, you will read that subdomains are not a way to avoid a bad domain reputation. Instead, they help you differentiate your traffic while maintaining a clear relationship with the main domain.