Error Details Error: 550 5.0.350 Remote server returned an error -> 552 message size exceeds maximum size tnmpmscs Message rejected by: <Mod remove PII>

Question

I try to send 33mb file but fail with this Error message :

Details Error: 550 5.0.350 Remote server returned an error -> 552 message size exceeds maximum size tnmpmscs Message rejected by: <Mod remove PII>

Answer 1

Hi Leslie Lau,

Thank you for posting your question in the Microsoft Q&A forum.

Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data.

Based on the NDR you shared, my understanding of your scenario is that you are using Classic Outlook with an Exchange Online (business) account to send an email that includes an attachment of approximately 33 MB to a recipient who appears to be using Yahoo Mail. The message was not delivered, and you received the NDR shown above.

I conducted a quick review based on this scenario and identified the following insights:

• From the sender side, Exchange Online does enforce message size limits. According to the Microsoft article Exchange Online limits, the default maximum message size for Microsoft mailboxes is 35 MB for sending and 36 MB for receiving. Administrators can configure a custom limit between 1 MB and 150 MB. This confirms that there are defined limits for message sizes within Exchange Online.
  
• However, in your case, the message was successfully sent from Exchange Online and only then generated an NDR, which indicates that the issue did not occur on the sender side. Further research shows that the error code “550 5.0.350” typically originates from the recipient’s mail server. For Yahoo Mail specifically, the maximum allowed size for an individual email message is 25 MB. This limitation is documented in Yahoo’s official help article: https://help.yahoo.com/kb/SLN5673.html
  Note: Microsoft is providing this information as a convenience to you. These sites are not controlled by Microsoft, and Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please ensure that you fully understand the risks before using any suggestions from the above link.

As a result, the message was rejected by the Yahoo mail server because the effective message size exceeded the recipient’s allowed limit.

Regarding possible workarounds, if you are acting as an end user, you may consider applying one of the suggestions already provided by the QA assistant above, all of which are valid and commonly recommended approaches. Among these options, the recommended best practice is to upload the file to cloud storage (such as OneDrive) and then share the download link with the recipient instead of attaching the file directly to the email.

Additionally, it is also advisable that the recipient verifies their mailbox storage usage, as a mailbox nearing or exceeding its quota may further contribute to message delivery failures.

I hope the information above is helpful.

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Answer 2

The error message you are encountering, "550 5.0.350 Remote server returned an error -> 552 message size exceeds maximum size," indicates that the file you are trying to send exceeds the maximum allowed size for email attachments on the recipient's server. In this case, the file size of 33 MB is too large for the Yahoo mail server to accept.

To resolve this issue, you can consider the following options:

1. Compress the File: Try compressing the file to reduce its size before sending.
2. Use a File Sharing Service: Instead of sending the file directly via email, you can upload it to a cloud storage service (like OneDrive, Google Drive, or Dropbox) and share the link in your email.
3. Split the File: If possible, split the file into smaller parts that are within the size limit and send them in separate emails.

Make sure to check the maximum attachment size allowed by the recipient's email provider, as this can vary.

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References:

• Fix NDR error "550 5.0.350" in Exchange Online
• "550 x-dg-ref header is too long" when sending mail in Exchange Online
• NFP maximum message size