You can attach Mailbox messages directly to a BP record. On any action form in the workflow, users can click on the link and view the referenced Mailbox. Attached Mailbox are added and viewed from the Linked Mail link at the bottom of the BP form. This link will show the number of emails, both Mailbox and external emails, that have been attached to the record. A single email message can be attached to more than one BP record.
Note: This option is available only in BPs that have been set up to accommodate linked Mailbox messages.