Postmaster Resources

Frequently Asked Questions

We currently do not publish a hard limit. We are constantly monitoring our mail flow for anomalies, and we review cases manually. If your mail is legitimate, then we will not take any action.

Any clearly malicious or unwanted emails may result in a manual block. We do not use automated systems for the Petalpost block list. If you are having to ask this question, it is highly likely that you are engaging in very clear spam activity. It may be possible, if you are on a shared host or IP range, that you are collateral damage from disruptive neighbors. You should consider a new host, but you may contact us to review the situation.

  1. Conform to RFCs. You can do this by using a proper MTA for outbound mail. Avoid sending email directly from your applications or programming libraries.
  2. Conform to industry standards for authentication:
    • Maintain appropriate reverse DNS for your mail host's IP. The hostname set in the reverse DNS should resolve to the IP address. It is also generally a good idea for the mail server's hostname used in SMTP transactions to match the reverse DNS hostname.
    • Utilize SPF, DKIM & DMARC.
  3. Keep your IP & domain off DNSBLs. We currently only utilize the Spamhaus DNSBLs, but your IP being found in any popular list is likely a sign of issues elsewhere.
  4. Don't attempt to send from dynamic or residential IP space. It might be fun to try and run a mail server at home, but unless you have cooperation with your ISP to remove you from dynamic IP address block lists, your mail will not be accepted.
  5. Follow best practices for list management. Emails in your subscription lists should never be there unless the user has explicitly agreed to be added. Having an account for your service is not enough.
  6. Be proactive. Keep an eye on your mail server logs for unexpected rejections. They may be the symptoms of a larger issue.
  7. Be responsive. We may occasionally reach out in good faith about an issue with your mail. Your postmaster or other publicly available contact addresses should be responsive and address concerns quickly.

No. Because we review cases of unwanted mail manually, we believe there is little benefit for a FBL. If there is legitimate mail with an issue, we will reach out regarding it.

Yes. We can receive mail from IPv4 and/or IPv6 capable hosts, and send to the same.

It stands for "Petalpost Mail".

SMTP Error Codes

Error Code Explanation
PPM-010 The email address you are attempting to contact is a service email and does not accept inbound mail. A human will not see messages to these addresses. If you have a concern, please contact us.
PPM-050 Your IP range has been blocked from Petalpost due to observed spam from addresses within your IP range. Our administrators have determined that blocking of the whole range is the most effective mitigation. Contact postmaster@kazehana.windflower.io to request an unblock.
PPM-051 Your IP address has been blocked from Petalpost due to observed spam. Our administrators have determined that blocking of your specific IP address is the most effective mitigation. Contact postmaster@kazehana.windflower.io to request an unblock.
PPM-052 Your mail server hostname has been blocked from Petalpost due to observed spam from your host. Our administrators have determined that blocking of your specific hostname is the most effective mitigation. Contact postmaster@kazehana.windflower.io to request an unblock.
PPM-053 Your IP address is listed in the Spamhaus ZEN list. Visit https://check.spamhaus.org/ to resolve this.
PPM-054 Your domain is listed in the Spamhaus DBL list. Visit https://check.spamhaus.org/ to resolve this.
PPM-055 Your domain is listed in the Spamhaus ZRD list, as it has been registered in the past 24 hours. Wait 24 hours and your domain will automatically be removed from this list.