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A header line of 100K bytes (spanning multiple continuation lines) should be adequate for valid email messages. Messages with longer header lines may well be malformed. They could even be deliberately malformed in an attempt to create a buffer overflow.
MailMarshal takes the safe approach and rejects any messages which exceed this limit. Increasing the limit could leave you vulnerable to a header exploit. If this issue occurs rarely, then the safest option would be to do nothing. If you are constantly getting this message or the source of the rejected email is known to be good, please contact LevelBlue Technical Support to discuss debugging and further configuration.
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