6.3.1: Share email does not work when started from homescreen icon

IOS / All Browsers 
http://mf-geoadmin30i.bgdi.admin.ch/
delete Cache
delete icons on homescreen
Start application 
Save link to homescreen
Start application from homescreen
-> Share
tap Share email

RESULT
only hint appears

EXPECTED RESULT
email client is opening


Workaround:
open application in Safari