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Sophos Data Control Rule 552 5.6.0 Headers too large (32768 max)


we have a problem that some Mails could not delivered to some recipients dut to a large Header. 

Error received 552 5.6.0 Headers too large (32768 max)

The Mails are sent via Office 365 over Transport Rules.

I would like to reduce the Header via a Data Control Rule, but i'am not quiet sure how to setup the Rule. 

I would like to create a rule which is editing header value, but not sure what to enter in value and header attribut.

Any suggestions? 

Thank you

Added TAGs
[edited by: Raphael Alganes at 11:26 AM (GMT -7) on 1 May 2024]
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  • Hi, 

    Thanks for the feedback, maybe I expressed myself wrong. It's not about the total size of the email, but about the headersize.

    • Message header size limits: Specifies the maximum size of all message header fields in a message. The size of the message body or attachments isn't considered. Because the header fields are plain text, the size of the header is determined by the number of characters in each header field and by the total number of header fields. Each text character consumes 1 byte.

    According to the text the Headersize exceeds the 32768 characters this must be a Headersize of 32KB in total.

    We have some Mail Flow Rues attaching Signatures for example and Microsoft ist adding a lot of stuff in the Header.

    Thank you