[exim] Avoid blank lines of the spamassassin spam report

I have EXIM installed on my server and implemented the control antispam with
SPAMASSASSIN, but all the spamassassin treatment it is done on an external
server, so my exim receives the 3 variables with the results of that
process: $spam_score, $spam_bar, $spam_report

The $spam_report variable contains some blank lines (due to the
configuration of the 10_default.conf template of the original spamassassin)

For example:

X-Spam-Report: Spam detection software, running on the system "XXXXXXXX",
has NOT identified this incoming email as spam. The original
message has been attached to this so you can view it or label
similar future email. If you have any questions, see
the administrator of that system for details.
-- BLANK LINE--
Content preview:
-- BLANK LINE--
Content analysis details: (-1.0 points, 5.0 required)
-- BLANK LINE--
pts rule name description
---- ---------------------- ------------------------ --------------------------
-1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP

The problem I have is that some mail clients do not interpret correctly
emails when there are blank lines in your header as in this case.

Since the antispam treatment is done on a server external to mine, I cannot
modify the template eliminating those blank lines.

As a solution it occurs to me within the exim delete in the variable
$spam_report blank lines, but ...
a) I don't know if Exim allows to do it
b) if exim allows to do it, I don't know how to do it ;(

Could someone tell me if it is possible to do it from exim and how?

Does anyone know if there would be another way to solve this problem?

Note: one of the alternatives I analyzed was to eliminate the inclusion of
the $spam_report variable in the header, but if possible I would like to
keep it.

Another alternative analyzed was to have the spam analysis process done on
my server, but I would be interested to continue doing it on that external
server to take advantage of the experience of its rules.

Thanks in advance.

Jorge Colaccini