[exim] Message rejected due to long Reference: header

Hello,

One of users complained at having their message rejected by our mail
server (Exim 4.91), providing the below server response:

"Mail delivery error. This email issue occurs because your email header
was rejected by recipient server.
The cause of rejection is because email reference header is more than
998 character. The 998 character limit is due to limitations in many
implementations that send, receive, or store IMF messages which simply
cannot handle more than 998 characters on a line. Receiving
implementations would do well to handle an arbitrarily large number of
characters in a line for robustness sake."

The user's emails contain:

X-Mailer: Microsoft Outlook 15.0

Is there any Exim setting capable of re-formatting long headers (i.e.,
split them into several lines, each below 998 character limit) etc such
headers, but allowing the incoming mail nonetheless?

We have quite long "threads" in local mail archives, with really many
References: entries, but still not exceeding 998 characters per line.

Sincerely,
Konstantin