Can I whitelabel messages without a dedicated IP?
At Postmark, using your own domain for Return-Path and DKIM is not only free but encouraged! This ensures all sender data shown in your recipients’ inboxes uses your brand.
There are, however, some required message headers that all Postmark mail must include. While this data will not be visible to your recipients in their inbox, receiving ISPs use these to identify and contact the Postmark team for security and anti-abuse purposes.