How to solve: Your message wasn't delivered because the recipient's email provider rejected it.

Question

It’s been two days since I can’t send me mails from my iPad because they are considered spam. The message I receive is:

Remote server returned '550 5.7.520 Message blocked because it contains content identified as spam. AS(9530)'

it only happens from my iPad, if I try to send the same email from my iPhone it works.

can anyone help me?

thanks

Answer 1

Hi Lu dt

I understand you can’t send emails from your iPad and receive the bounce “550 5.7.520 Message blocked because it contains content identified as spam. AS(9530)”, while sending the same email from your iPhone works.

Are you sending from the Outlook app on iPad or the built-in iOS Mail app, and does the failing message include an attachment? 

Meanwhile, please follow these steps if the AI steps do not work:  

• Force the iPad client to resend using a different message format (avoid HTML if possible) 
  • Some 5.7.520 spam blocks are triggered by how a message is formatted. Switch a message to Plain text in Outlook. Try sending the same email again after switching the format to plain text.  
• Reset the Outlook account on the iPad (does not require deleting the account) 
  • If you are using the Outlook app on the iPad, use Reset Account. After the reset, try sending again.  
• Bypass the iPad app temporarily by using an alternate Microsoft-supported client path on the same device 
  • Add the same mailbox to the built-in iOS Mail app using Set up an Outlook account on the iOS Mail app - Microsoft Support setup steps, then test sending from there.  
• If you are trying different apps/devices, add an Outlook.com account to another mail app/device. 
• If the block starts happening from multiple devices (not just the iPad), use Microsoft Sender Support  
  • If you later notice the same 5.7.520 block happens from other devices too, use Sender Support in Outlook.com to address deliverability/reputation factors.  

Please tell me how it goes. If the problem persists, please don’t hesitate to reply to this thread and I will be happy to help. Have a lovely day!   

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Answer 2

I had the same problem. I’ve been able send links to articles and/or images for years from my iPad to my Hotmail account and they recently stopped working with the error described above. I tried sending them to my Gmail account and they worked fine. I could forward them from the Gmail account to the Hotmail account without any problems. I deleted the default signature that Apple installed on my iPad and things started working.

Answer 3

The error indicates that the recipient’s mail system is classifying messages sent from the iPad as spam and rejecting them with SMTP code 550 5.7.520. Because the same message works from the iPhone, the issue is specific to how mail is being sent from the iPad (client-side behavior or configuration), not to the Outlook.com account itself.

Use these targeted steps on the iPad:

1. Check message content and attachments
   • Remove any large attachments and test sending a simple text-only message to the same recipient.
   • If the simple message is delivered, gradually add back the original content/attachments to identify what triggers the spam classification.
2. Review and simplify the email signature on iPad
   • Signatures can sometimes impact the ability to send mail. If an error occurs, remove the signature from the email and resend.
   • Compare the signature configured on the iPad with the one on the iPhone and align them.
3. Send to a different recipient and to self
   • Send a test message from the iPad to the same Outlook.com account (self) and to another provider (for example, a different personal address).
   • If only certain domains reject the message, their spam filters are specifically blocking the pattern generated by the iPad client.
4. Check for known client-side issues on Apple devices
   • There are known cases where Apple mail clients cause server-side rejections or misleading errors (for example, large attachments causing “message rejected by the server” or “mailbox is full” from Exchange). Microsoft has identified such issues as client-side and directs users to contact Apple Support for a fix.
   • If the problem persists only on the iPad after checking content, signature, and attachments, contact Apple Support to review the Mail app configuration and any device-specific bugs.
5. If using Outlook for iOS on iPad
   • Make sure the Outlook app is fully updated.
   • Remove the Outlook.com account from the Outlook app on the iPad and add it again, then test sending.
6. If using Apple Mail with an Outlook.com account
   • Remove the Outlook.com account from iPad Settings → Mail → Accounts, then re-add it using the Outlook.com/Exchange option and test again.

If, after these steps, messages from the iPad are still rejected as spam while the iPhone continues to work, the behavior is consistent with a client-side issue on the iPad and should be escalated with Apple Support, providing them the full error text including 550 5.7.520 and AS(9530).

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References:

• "Cannot Send Mail - Your mailbox is full" error when you use iPhone mail to send very large attachments (KB5004622)
• Can't send or receive email in Outlook.com
• Sent email in Outlook.com comes back "delivery failed"
• Message Trace FAQ in Exchange Online
• Outgoing emails with attachments undelivered as spam - Microsoft Q&A
• Stopped receiving emails on my account. - Microsoft Q&A
• Outlook email filter issue - Microsoft Q&A