When trying to enter an email address that already exists in the system a message will appear
'A patient who is not a family member has this email address. Email addresses can only be shared by patients within the same family. Please enter an email address that does not belong to a specialist or a patient who is not a family member.'
You can add the same email address as another patient if the other patient/s are part of the same family (see: Adding/Removing Family Members)
The message will usually say which patient/s currently share the same email address so you know who you need to search for but If you are not sure or want to search for all patients that share the same email address, click on the magnifying glass at the top of the patient file and search for the email address to reveal which other patients currently have the same email address set. You can delete the email address from other patient files then try adding it again.