Changing email for the account owner
The account owner is responsible for managing users in Fathom. As an account owner, you can change your own email address if required.
You'll just need to login to Fathom on your old email address, and invite yourself in on your new email address. Then you will be able to switch your access rights over to your new address.
Here are the steps on your end:
Login to Fathom
Select the administration menu (cog icon) on the top right, and then select 'User Management'
Select 'Invite a person' and invite yourself in again as an Admin user
Click the activation link in your email to activate your new address
Go back to Fathom, and again, select the administration menu (cog icon) on the top right, and then select 'Account/Billing'
Under the 'Transfer My Account' dropdown, you can now make your new address the 'account holder'
You can then delete your old email address from User Management if you like.
Changing email for other users
If a Fathom user needs to change their email address, an admin user can simply invite them in on their new email address, and then delete their old email from User Management.