A Catch-all email address provides ProtonMail custom domain users the option to receive all mail sent to their domain, even if they are sent to an email address that has not been set up for their domain. It is a feature currently only available for Visionary and Professional ProtonMail account holders.
If you don’t have a Catch-all address enabled and a sender tries to send a message to an incorrect address, they will receive a bounce-back message informing them that the address they tried sending to does not exist within your domain.
Your message wasn't delivered to firstname.lastname@example.org because the address couldn't be found. Check for typos or unnecessary spaces and try again.
How to enable a Catch-all email address
1. Ensure you have completed all of the steps to set up your custom domain and addresses.
2. Go to Settings → ProtonMail → Identity & addresses to see a list of all addresses associated with your ProtonMail account.
3. To enable Catch-all, go to Settings → ProtonMail → Domain Names. In the dropdown Actions menu, select Set catch-all and you will be asked to input an email address belonging to your domain.
All mail sent to your domain that does not match an address in your account will now be delivered to this address.
Tip: To prevent Catch-all email messages from cluttering up your Inbox, we recommend creating a dedicated address within your domain to deliver all Catch-all email messages to (for example, email@example.com or firstname.lastname@example.org).