Gmail has made a change to help identify spoofed emails and verify sender identities in inboxes. The "via" label, added to the 'From' address field for third-party senders like Postmark, provides information about the return-path domain used by these senders. To prevent this label from displaying, users can sign their messages with DKIM, a process made easy by Postmark's tools and support. For customers sending emails on behalf of others, a simple HTML page explains the purpose of the "via" label, aiming to reduce confusion for recipients.