[Exim] Format error in spool file

I have three messages in my queue which are showing "Format error in spool file"
errors in eximon and the mainlog. The common feature is that stands out to me is
that they have accented characters in the HELO hostname.

Could this be the cause?

If so then there is a problem with having helo_accept_junk_hosts letting them
through.

Phil.
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Phil Chambers (postmaster@???)
University of Exeter