550 #5.7.1 SPF unauthorized mail is prohibited

If you attempt to send an email to an iiNet email address and you receive an "550 #5.7.1 SPF unauthorized mail is prohibited" error, this means that your email account is failing a Sender Policy Framework (SPF) check.

SPF is a set of rules for defining who/what is allowed to send email for an email domain, and what to do with the email if it fails. This helps protect email senders and recipients from spam, spoofing, and phishing.

Not all mail providers choose to honour SPF, so when issues arise as a result of SPF configuration, you will find not all email is impacted. Due to the benefits, iiNet honours the SPF instructions set by external mail providers, the typical action requested is to either block the mail or deliver it with a suspicious content flag. When SPF records are malformed or broken, we treat all mail from the affected domain as suspicious.

What to do if you receive an "550 #5.7.1 SPF unauthorized mail is prohibited" error when emailing an iiNet address

  • You must contact your email hosting provider or email technician to resolve the issue.
  • iiNet cannot change the SPF records for any email services except those that we provide.
  • You may be able to assist your email hosting provider/email technician by checking your email domain (e.g. "gmail.com") in a public SPF record checker such as the DMARC Analyzer SPF Record Checker. This check may provide more information to help your email hosting provider/email technician understand how they must update their SPF record to resolve the issue.

If you would like to read more about SPF and how it works, DMARC Analyzer have a great article on Everything you need to know about SPF.


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