Once you have completed the setup to send email from your own address, you may notice that at first your emails are either going to recipients' junk folder or are being blocked by the recipient's internet service provider (ISP). Why is this?
- Proprietary Spam Filters
- Each client's provider uses internal algorithms that weigh factors like sender reputation, authentication alignment (SPF, DKIM, DMARC), message content, links, attachments, and even user behavior (such as if users mark things as junk).
- These algorithms are not public and can change without notice.
- Sender Reputation is Domain- and IP-Specific
- Even if Postmark, the service we use to send emails, is a reputable sending service, a new domain or sender signature might not yet have a strong sender reputation.
- Until the domain proves it sends legitimate, non-spammy emails, it might be treated cautiously or flagged. This is why deliverability improves after your emails are moved out of Junk or marked as not junk several times.
- Some ISPs Are More Aggressive
- Outlook, in particular, has tighter spam filters and may route legitimate emails to Junk, especially from domains it doesn’t recognize or trust yet.
- Some corporate or government providers have custom firewalls or blocklisting policies that are even stricter. If this applies to your organization—or your customer's organization—please work with the appropriate IT team to ensure your domain is allowlisted.
- We Can’t Override ISP Behavior. As a third-party sender (via Postmark), we do not have the ability to bypass or override ISP rules. Our role is to:
- Ensure the email is authenticated (SPF, DKIM, DMARC)
- Monitor sending reputation
- Avoid spam-triggering content. But final delivery is controlled entirely by the recipient’s email provider, and sometimes their individual settings.