Postmark May 2026

Depending on whether you're looking for information on the postal stamp itself or the transactional email service, here are highly-rated articles and guides for both: The USPS Postmark (Mailing Deadlines)

To send the email, you pass a JSON "TemplateModel" through the Postmark API postmark

💡 Pro Tip: Use a subdomain (like ://yourdomain.com) for Broadcast streams to keep your primary domain's reputation safe for critical transactional mail. Depending on whether you're looking for information on

• Keep transactional and marketing emails on different streams/IPs.

There are several types of postmarks, including: There are several types of postmarks, including: