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My Exchange 2016 server is rejecting an incoming SMTp message with error:

Remote Server returned '550 5.2.3 RESOLVER.RST.SendSizeLimit.Org; message too large for this organization'

I confirmed that the site, Exchange receive connector, and recipient mailbox have 25MB size limits. However, this message is only 8MB size (+MIME overhead so x1.37).

Can someone explain where else I can check to resolve this?

TSG
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  • Hi, it's been a long time, is there any update? If the issue has been fixed, you could mark the best answer to help more people who have the same problem. Have a nice day:) – Ivan_Wang May 19 '20 at 06:22

1 Answers1

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According to the undeliverable message(Enhanced Status Code 5.2.3), the issue could be caused by the following Message size and recipient limits:

  1. MaxReceiveSize value of one mailbox(Get-Mailbox -Identity "Mailbox Name" | fl MaxReceiveSize).

  2. MaxMessageSize and MaxRecipientsPerMessage values of the receive connectors(Get-ReceiveConnector | fl MaxMessageSize, MaxRecipientsPerMessage)

  3. MaxReceiveSize and MaxRecipientEnvelopeLimit values of organization limits(Get-TransportConfig | fl MaxReceiveSize, MaxRecipientEnvelopeLimit)

  4. Check whether some Transport Rules are blocking the email messages which have large attachment size and message size(Get-TransportRule | fl Name, AttachmentSizeOver,MessageSizeOver).

If the size of incoming message is beyond the above limits, you could try to increase these limits by referring to the following links:

Wait for a while after modifying these limits, then receive the incoming messages again to check the result, if still not work, it seems that the sender has configured some limits of the message delivery.

Ivan_Wang
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