问题 Our outlook add-in works in most scenarios on a shared Mailbox, except when the attachment in an email is of type " Office.MailboxEnums.AttachmentType.Item " e.g " .msg " file. Environment is Outlook web and desktop. We mostly get all attachment content via REST, as they are returned as base-64, but with " AttachmentType.Item " the body is email body and not a base-64. In this case, we make a call to EWS to download that attachment, process the body and return as byte[]; The problem we are