I have my OX running behind a SSL Firewall from Sonicwall. After updating to 6.20 I noticed the same problem of a missing/incomplete OX login as soon as the connection was made thru the SSL Firewall. (see: https://forum.open-xchange.com/showt...hlight=deflate)

As the SSL Firewall is a bit older, it turned out that it does not understand the "AddEncoding gzip .jsz .cssz .xmlz" command correct.

I had to edit /etc/apache2/sites-available/default and replaced the

"AddEncoding gzip .jsz .cssz .xmlz"
by
"AddEncoding x-gzip .jsz .cssz .xmlz"

Now all works fine.