[exim] Terminal corruption with DKIM information lines from …

Hello

When tailing exim logs, I am seeing terminal corrupting characters in DKIM
information lines, but only from mailjet.com hosts.

Some examples:

2018-03-19 08:29:27 1exqAZ-0007wD-Rd DKIM: d=bnc3.mailjet.com s=mailjet
c=relaxed/simple a=rsa-sha256 b=1024 i=^^?>^l^`^`N^t3Z*k5^l$.^`]

2018-03-19 08:35:04 1exqG0-0008Uc-7V DKIM: d=bnc3.mailjet.com s=mailjet
c=relaxed/simple a=rsa-sha256 b=1024
i=$8^`^`^`^`^`^`^`^`^`~^{'^`#^`^`w^c{^`e^`z^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`
^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`
^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`

In other cases, it appears the message content is leaking into the log:

2018-03-19 08:34:13 1exqFB-0008HR-Lr DKIM: d=bnc3.mailjet.com s=mailjet
c=relaxed/simple a=rsa-sha256 b=1024 i=lspacing=3D"0" width=3D"100%" border
b=10 [verification succeeded]


Whatever the problem is, it's always after the "i=" section, and it's only
ever from this domain.

This is with Debian's exim 4.89-2+deb9u3. Any ideas?

Thanks

Martin.