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Cisco Bug: CSCuw09558 - Large Ironport-PHdr header does not fold causing delivery problems

Last Modified

Sep 03, 2021

Products (1)

  • Cisco IronPort Email Security Appliance Software

Known Affected Releases

10.0.0-203 10.0.1-087 13.0.0-392 13.5.2-036 9.6.0-042 9.6.0-047 9.7.1-HP2-207

Description (partial)

Symptom:
Some emails may contain an non-folded 'Ironport-PHdr' header that exceeds the limit for line length specified in RFC5322.  This large header can cause delivery issues depending on how the receiving mail server interprets the header.  This header can cause mail servers to reject the mail, misinterpret the mail, or behave unexpectedly during delivery.

Conditions:
Long Ironport-PHdr headers have been known to occur on messages with large numbers of recipients.

Related Community Discussions

Message header limits on Ironport
I am getting issues on a RELAY mail flow policy where messages are being aborted with the error "Message header too big." What is the default limit for message header sizes and how can you change it for particular senders?
Latest activity: Dec 22, 2016
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  • Status
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