Below are the instructions to setup your gmail account with domain names.
It will allow you to create and reply with your domain name in the from address.
Below assumes you already have setup your own domain name
Before setting up Gmail with domain name you will need to setup the security.
login to google
Go to "Manage your Google Account"/Security
Setup 2-step Verification if you this has not been done.
Go to https://myaccount.google.com/apppasswords to setup an App password
Click on "Select App" and chose Other
Type in a name example abcxyz.com
Click on "Generate"
You will be presented with a password which will be used in step 10 below
The App password seems to expire after 12 months.
This is a good thing as it is best practice to rotate your passwords on a regular basis.
Create domain
Add Email forwarding for the domain.
Example:
Domain: abcxyz.com
Forward the email john.smith@abcxyz.com to john.personal@gmail.com
Login to your gmail account
Go to Gmail Settings in the top right corner and select see all setting
Select Accounts and Imports
In the section "Send mail as: " click on "Add another email address"
Enter name and the domain name email address eg john.smith@abcxyz.com then click next step
Enter the smtp address "smtp.gmail.com" and port "587"
Enter the username which is the full gmail address eg john.personal@gmail.com
Enter the password. The password is from the "Manage your Google Account"/Security/App passwords (https://myaccount.google.com/apppasswords)
Click on Add Account. Google will sent email to john.smith@abcxyz.com which should appear in the inbox of john.personal@gmail.com
and ask you to put in the verification code.
Enter the verification code and verify.
Log out and log back into john.personal@gmail.com
You can now create a new email and select the from address as john.smith@abcxyz.com