Support » Plugin: Post SMTP Mailer/Email Log » TEST Mail delivery via IONOS SMTP not working

  • Tobo


    Hi there,

    I have used the test mail to check if IONOS SMTP is working. The test mail was not delivered because of:

    554 Transaction failed, reject due to policy restrictions

    The email was rejected by the IONOS SMTP server because the standards defined in RFC 5321 and RFC 5322 were not adhered to.


    The email client must meet the following criteria:

    The header lines of the email must contain exactly one valid “Date” line according to RFC 2822.
    The following header lines may only exist once: From, Sender, To, CC, Subject
    The header lines mentioned must be syntactically correct
    Note: The To and CC lines can contain multiple recipients.

    In accordance with the recommendations from RFC7103, incorrect messages are not automatically corrected by IONOS, otherwise DKIM signatures become invalid. For more information about DKIM signatures, see the IONOS article Configuring DMARC Records for a Domain.

    So I thought it isn’t working. But it is working, because Woocommerce Mails are delivered without that error…

    FYI :).


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