Optusnet authentication to outlook

wayne bryan 0 Reputation points
2026-06-12T05:51:50.9+00:00

outlook/Hotmail doesn't except emails from optusnet.com.au

shows sent nobody reiceves.

error message: SMTP error from remote mail server after pipelined end of data:

    550 5.7.515 Access denied, sending domain OPTUSNET.COM.AU doesn't meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender

Outlook | Web | Outlook.com | Email
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  1. AI answer

    2026-06-12T05:52:07.02+00:00

    The error means Outlook.com is rejecting messages from optusnet.com.au because the Optusnet sending domain does not meet Microsoft’s required email authentication level for high‑volume senders.

    Microsoft now enforces stricter authentication for large senders to Outlook.com/Hotmail and other Microsoft consumer services. Once a domain sends 5,000 or more messages to Microsoft consumer mailboxes and uses the same domain in the 5322.From address, all messages from that domain must:

    1. Publish SPF and DKIM records for the domain, and both SPF and DKIM checks must pass.
    2. Publish a DMARC record for the domain (for example: Hostname: _dmarc, TXT value: v=DMARC1; p=none).
    3. Pass DMARC validation, where SPF and/or DKIM align with the domain in the 5322.From (From) address.

    Because this is enforced at the domain level (optusnet.com.au), this is not something that can be fixed from Outlook.com or the individual mailbox. The owner/operator of the optusnet.com.au domain (Optus) must:

    1. Check message headers to see SPF, DKIM, and DMARC results and ensure the return‑path (5321.MailFrom) domain aligns with the 5322.From domain.
    2. Configure or correct SPF, DKIM, and DMARC DNS records for optusnet.com.au so that messages pass DMARC alignment.
    3. Ensure any third‑party sending services used with optusnet.com.au are configured to use that domain in 5321.MailFrom and DKIM signing, and are included in the domain’s SPF and DMARC configuration.

    Until Optus updates the domain’s authentication to meet these requirements, Outlook.com/Hotmail will continue to reject messages with this 550 5.7.515 error.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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