What does SMTP code 550 SPF HardFail on outgoing e-mail mean?
Oracle B2C Service, All versions
Our outgoing e-mails are failing to reach certain domains. The bounce error is:
"550 SPF Hard Fail: Domain Example.com does not designate Example-IP as permitted sender."
This occurs each time the outgoing e-mail is spoofed and the recipient domain is configured to reject SPF failures directly. Basically, the SPF record fails to pass the check because the sender's domain (used in the From-Address) does not have the 'rnmk.com' domain inclusion within the record. This way, the e-mail is sent using your branded address / domain name, while the originating IP belongs to Oracle.
You can test the SPF check towards the Gmail domain. This domain is more permissive and will allow the e-mail to come in even if the message fails the check.
In order to fix the behavior, you will need to follow the article below and update your SPF record accordingly. Information to achieve this can be found in the following knowledge base article: Answer ID 2489: SPF and Sender ID considerations with Oracle B2C Service sites.