Basic Setup:

wget -O - https://get.acme.sh|sh

Issue Certs using acme.sh, adding autodiscover as a SAN with mobile.domain.com beeing your GMX server dqqdn

acme.sh --issue -d mobile.domain.com --standalone -d autodiscover.domain.com

If you receive an error about missing netcat(nc), even though netcat is installed, install netcat-openbsd through YAST and try again.

This will create a cron entry that will run every nicht, but only generate new certs every 60 days.

#certs will be downloaded to ~/.acme.sh/mobile.domain.com/

To create the cert that GMS can use:

cat ~/.acme.sh/mobile.domain.com/mobile.domain.com.key ~/.acme.sh/mobile.domain.com/fullchain.cer > ~/.acme.sh/mobile.domain.com/server.pem;

I added this bit to see if the file has changed from last time, and if it hast, vopy to where GMS can see it and restart GMS

ck1=`md5sum ~/.acme.sh/mobile.domain.com/server.pem|awk -F" " '{print $1}'`;
ck2=`md5sum /var/lib/datasync/device/mobility.pem|awk -F" " '{print $1}'`;

if [ $ck1 != $ck2 ]
then
        /bin/cp -f ~/.acme.sh/mobile.domain.com/server.pem /var/lib/datasync/webadmin/server.pem;
        /bin/cp -f /var/lib/datasync/webadmin/server.pem /var/lib/datasync/device/mobility.pem;
        /usr/sbin/rcgms restart;
fi;