Email Address Sharing
Email address sharing gives you the ability to associate a single email address with multiple contact records, which allows a group of related contacts (such as a family or a team) to maintain individual contact records while sharing an email address.
For example, Bill Short and Bill Short can share the same email address as long as they have different logins.
If multiple contacts’ logins are left blank, their first or last name must be unique. In this case, Bill Short and William Short can share the same email address, since each name is unique.
Email addresses associated with a single contact record must be unique—that is, for a single contact, the values of contacts.email, contacts.email_alt1, and contacts.email_alt2 cannot contain the same address.
After email address sharing is enabled, records and transactions initiated by a shared email address are associated with the contact considered to be the best fit. The contact-matching process used to determine the best fit is shown in this flowchart.

When shared contact addresses are in different fields (for example, contacts.email_alt1 and contacts.email_alt2), the system selects the contact whose address is in the field of highest precedence (contacts.email_alt1). However, if the shared addresses are in the same field (for example, both are in contacts.email_alt1), the system attempts to match the values in the First Name and Last Name fields if available. If no match is found based on field precedence or name values, the system selects the contact record last updated in the database.