Email and attachments, some attachements disapear in mail client.

[L.P.H. van Belle]

Hai, 
 
I have a problem with recieving email attachements. 
 
The current system is running: 
Operating System Version: Debian GNU/Linux 9 (stretch)
MailWatch Version: 1.2.12
Postfix Version: 3.1.12
MailScanner Version: 5.1.3
ClamAV Version:
SpamAssassin Version: 3.4.2
PHP Version: 7.0.33-0+deb9u6
MySQL Version: 10.1.41-MariaDB-0+deb9u1

After a customer upgraded its exchange to 2019 im loosing attachments. 

I noticed if they send an email to userA and CC it to userB withing the same network and email domain. 

UserA, does NOT see the attachment (xls) and the userB does have a the xls files in the email. 
What i also notice, in mailscanner/mailwatch, userA shows "winmail.dat" file, userB shows the xls file. 

UserA never sees any attachments. 

Im suspecting it involves these settings, i already attempted to set change : 
Use TNEF Contents = replace to add. 

Expand TNEF = yes
#Use TNEF Contents = replace
Use TNEF Contents = add
Deliver Unparsable TNEF = yes

TNEF Expander = /usr/bin/tnef --maxsize=350000000
TNEF Timeout = 120

Am i missing something here? I can figure out what is going on here.

Suggestions? 

Greetz, 

Louis