To add allowed domains to your workspace:
Navigate to the top right corner of Synthesia and select your user icon.
Click on Preferences.
On the User settings page, select the Collaboration tab.
Select the Open for anyone with a certain domain option.
Insert your company's domain, which will allow users with email addresses from that domain to join the workspace directly by signing up to Synthesia through the website.
Notes:
Only email domains used by existing workspace members can be added.