My Email Keeps Bouncing

Question

How do I fix it as the message it keeps sending back is

Delivery has failed to these recipients or groups:

******@storyofhome.co.uk This message couldn't be delivered because the sending email address was not recognized as a valid sender. The most common reason for this error is that the email address is, or was, suspected of sending spam. Contact the organization's email admin for help and give them this error message.

Diagnostic information for administrators:

Generating server: LO0P265MB7060.GBRP265.PROD.OUTLOOK.COM

******@storyofhome.co.uk Remote server returned '550 5.1.8 Access denied, bad outbound sender AS(42004)'

Original message headers:

Received: from LO0P265MB7060.GBRP265.PROD.OUTLOOK.COM
 ([fe80::99b3:c5e2:c972:1979]) by LO0P265MB7060.GBRP265.PROD.OUTLOOK.COM
 ([fe80::99b3:c5e2:c972:1979%6]) with mapi id 15.21.0092.011; Sun, 7 Jun 2026
 20:51:02 +0000
MIME-Version: 1.0
Content-Type: text/plain
Date: Sun, 7 Jun 2026 20:51:02 +0000
Message-ID:
       <******@LO0P265MB7060.GBRP265.PROD.OUTLOOK.COM>
Subject: Quick Question For Story Of Home

Answer 1

The bounce message shows error 550 5.1.8 Access denied, bad outbound sender AS(42004). This means the sending address has been flagged as a bad or spam sender and is being blocked.

Since this is an Outlook.com / Outlook on the web scenario, use these steps:

1. Verify the recipient address and resend
   • Open the non-delivery (bounce) message.
   • Use the “Send Again” option if available, or create a new message.
   • In the To box, delete the existing recipient entry.
   • Start typing the recipient’s address, select it from Auto-Complete, and delete that entry so any bad/outdated cache is removed.
   • Type the full recipient address again carefully and send.
2. Check for other common delivery issues
   • If the bounce ever mentions:
     • Host unknown / Domain lookup failed: confirm the domain (e.g., storyofhome.co.uk) is spelled correctly.
     • Mailbox not found / User unknown / Mailbox unavailable: confirm the recipient gave the correct address and that it still exists.
     • Message too large: reduce attachment size or upload files to OneDrive and send a link.
3. Improve the sender’s spam reputation
   • If the address or its sending IP has a low spam reputation, Outlook.com can block it:
     • If anti-virus has “Internet Email Auto Protect/Protection” enabled, temporarily disable that and send a test message.
     • Ensure the “From” name is clearly identifiable (not blank or suspicious).
     • Send an email to the same account, open it, and reply to it.
     • Add frequent correspondents to Contacts so their replies and interactions help reputation.
4. If the problem persists
   • The message text explicitly says to contact the organization’s email admin. Provide them the full error, including 550 5.1.8 Access denied, bad outbound sender AS(42004) so they can:
     • Check whether the mailbox or tenant has been flagged for spam.
     • Review outbound spam policies and any blocks in Microsoft 365.
   • For consumer Outlook.com accounts, use Outlook.com in-browser Help:
     • Select Help in Outlook.com, describe the delivery failure, and follow the “Still need help?” path to contact support.

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References:

• Sent email in Outlook.com comes back "delivery failed"
• Failed delivery messages from the postmaster at outlook.com, microsoft.com, or service.microsoft.com
• Sender Support in Outlook.com