Step 1: Collect the domain or subdomain you would like to use for your mailing address
Top domain providers – How to add a subdomain articles:
GoDaddy - https://www.godaddy.com/help/add-a-subdomain-4080
Digital Ocean - https://docs.digitalocean.com/products/networking/dns/how-to/add-subdomain/
Host Gator - https://www.hostgator.com/help/article/what-is-a-subdomain-name-how-do-i-create-and-delete-one
Blue Host - https://www.bluehost.com/help/article/subdomains
Step 2: Navigate to Account Settings > Email Settings
Step 3: Find the Email From Domains Section
Step 4: Click the purple + Button
Step 5: Type in the domain or subdomain you would like to send emails from
Enter the domain name you would like to send from. You must have access to this domain's DNS records in order to verify ownership.
You will not be able to send from an unverified domain name.
You will be able to send from any email address at this domain. For example, if you add the domain "my.widgets.com", you will be able to send from user1@my.widgets.com.
For marketing purposes, it is recommended to use a subdomain. For example, if your domain were "widgets.com" and your email address was "user@widgets.com" then it would be recommended to use a subdomain such as "send.widgets.com" for marketing and automations.
Step 6: Click Save & Close
Step 7: Copy and paste all the TXT type entries to your DNS records
Bluehost example
These images are from the Bluehost DNS TXT Entry and are meant to provide an example. Please follow the process that applies to your domain host provider.
Add New TXT Entry
All TXT Entries Present on DNS Records
Step 8: Verify the records (may take up to 24 hours)
The domain must be verified before it can be used to send messages from. This could take up to 24 hours. So, if you get an unverified message check back in a while and try again.