Logging headers of haproxy 2.2 + exchange 2016 + 401 POST /mapi /EWS

I am having similar problems as discussed here[1]. I guess the htx cannot be disabled anymore in 2.2? (although a reload does not say anything about it being deprecated)

Most of the mapi requests are 200

These urls are giving 401
POST /EWS/Exchange.asmx

Here it looks like outlook keeps trying and eventually succeeds

.
     0/0/2/5/7 401 247 - - --VN 20/9/5/4/0 0/0 "HEAD /OAB/cd520fd1-051d-    4d82-b235-70504e60db7b/oab.xml HTTP/1.1"
     0/0/0/2/2 401 247 - - --VN 20/9/5/4/0 0/0 "HEAD /OAB/cd520fd1-051d-4d82-b235-70504e60db7b/oab.xml HTTP/1.1"
     0/0/0/1/1 401 508 - - --VN 20/9/6/5/0 0/0 "HEAD /OAB/cd520fd1-051d-4d82-b235-70504e60db7b/oab.xml HTTP/1.1"
     0/0/0/97/97 200 648 - - --VN 20/9/6/5/0 0/0 "HEAD /OAB/cd520fd1-051d-4d82-b235-70504e60db7b/oab.xml HTTP/1.1"
     0/0/0/26/26 200 23849 - - --VN 20/9/6/5/0 0/0 "GET /OAB/cd520fd1-051d-4d82-b235-70504e60db7b/oab.xml HTTP/1.1"
.

Here someone is writing it can be due to the headers. How can I have haproxy log these 401 headers to syslog or so?

I have put this in the frontend, yet 200 are still logged.
http-request set-log-level silent if { status 200 }

[1]

[2]