The “Correspondent” field is located at the left-hand side while viewing a case.
It is used to contain the email address of the external customer or client who’s emailed about a question, bug, issue, or feature. Any case edits (adding a comment, changing the values of other fields, etc.) performed by a Manuscript User (Admin or Normal) will not generate a notification to the Correspondent. The Correspondent will only receive emails about the case if and when a Manuscript user (Normal or Admin) clicks “Reply”, “Forward”, or “Email” on the case and then clicks “Send” or “Send & Close”.
It can also help you find related emails from the same client or customer, or company.