Hello @allypitman ,
Thank you for your message.
Post SMTP shows the email as “Sent Successfully” because your mail service accepted the message without any errors. However, Yahoo performed its own checks afterward and bounced the email, which happens outside Post SMTP’s control.
A bounce from Yahoo typically indicates issues such as:
- SPF/DKIM/DMARC not fully aligned
- The “From Email” not matching the authenticated domain
- Yahoo filtering or blocking the sending IP/domain
To identify the exact cause, please share the bounce message you received. That will tell us precisely why Yahoo rejected it and how to fix it.
Happy to help you resolve this.
Support Team – WP Experts
the bounce back email had this message (I’ve taken out the persons email:
the email address
   host smtp-relay-float.mail.stackcp.net [10.4.0.246]
   SMTP error from remote mail server after RCPT TO:<email address>:
   550-“Please enable DKIM for your domain. Yahoo requires all senders to
   550 authenticate with DKIM – https://senders.yahooinc.com/best-practices/“
Reporting-MTA: dns;Â smtp1.lhr.stackcp.net
Action: failed
Final-Recipient: rfc822; the email address
Status: 5.0.0
Remote-MTA: dns;Â smtp-relay-float.mail.stackcp.net
Diagnostic-Code: smtp; 550-“Please enable DKIM for your domain. Yahoo requires all senders to
550 authenticate with DKIM –Â https://senders.yahooinc.com/best-practices/“
But further emails sent, have been received by the intended recipient
Hello @allypitman ,
Thank you for sharing the bounce details.
Yahoo rejected that specific message because your domain did not have DKIM enabled or passing at the time the email was sent:
550: “Please enable DKIM for your domain. Yahoo requires all senders to authenticate with DKIM.”
