Sending Domain Name is a domain which indicates from whom an email campaign is sent via “From:” header. For example: In screenshot given below; “easysendy.com” is the sending domain name.
You should add and verify this domain name in your SMTP email delivery provider dashboard, and this domain will be used to send emails from your Ariticmail and your delivery server account.
For example, if you would like to send an email campaign from email address – marketing@google.com then, you should add and verify ownership of domain google.com in your SMTP delivery server provider setting. To verify these domains in your relay provider setting; you will need to add and verify some TXT / CNAME records on your domain name.
Once can use as many different sending domains or from addresses from Ariticmail account; only condition here is your sending domain name should be verified inside the delivery server provider account.
For right technology setup, you should add DKIM, SPF and DMARC records to your sending domain name as provided by the SMTP relay service provider.
Do not try to send emails from a domain you do not have (own).