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Has anyone seen a bounced email because of the header size?

My Cisco Ironport appliance receives the following NDR when sending emails to Office365.

bounced by destination server. Reason: 5.3.0 - Other mail system problem ('554', ["5.6.211 Invalid MIME Content: Single text value size (32837) exceeded allowed maximum (32768)

Run.Bat
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  • What did you do to verify your headers are properly folded? – anx Mar 03 '21 at 23:26
  • I found out after I posted this that Ironport has bug and does not fold the header correctly. I'm going to have to create a policy to strip it out. – Run.Bat Mar 04 '21 at 15:01

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