You can set your custom domain to be used with ProtonMail to create a truly personalized secure email experience.
Once you have acquired your own domain and upgraded to a premium ProtonMail plan, you can go to Settings -> Domains to add your domain.
After adding the domain name, you can follow the setup wizard, which involves changing your domain’s DNS records. Once you have completed the required steps (Verify, Addresses, and MX), you will be able to send and receive emails in your account using the custom domain addresses that you have set up!
We recommend setting up Anti-spoofing on your custom domain for added security, and for preventing your address to be abused.
Below are some additional articles to assist you while setting up ProtonMail Professional accounts:
[You are currently here] Step 1: Setting up Your Domain(s)
Step 2: Creating your Organization
Step 3: Setting up User(s)
Step 4: Migration of existing email messages (Coming 2018)