Using one email address for multiple Practice Ignition accounts is currently not supported although this is something that we're looking into.
If you're using Google as your email provider, you can take advantage of their feature that allows you to create an alias for your email address. This will seem like your using multiple email addresses but in reality, you're only using one.
To do this, simply add +(desiredaliashere) between your real user name and the domain name. e.g. firstname.lastname@example.org
Read more about Google alias here.
If you're not using Google as your email provider, please contact your admin/ IT person who can set-up a proper alias for you. Once created, reach out to our Support team at email@example.com so we can change the log-in into the new email address.