You can use DNSSEC in ISPConfig, just not the automatic zone mirroring. Use the secondary DNS feature instead.
As a use Openprovider i can't use the DNSSEC from ISPconfig. Iam discussing an option with openprovider for a period of 3 months using the old unsafe (according to Openprovider) Algoritm. Maybe they will contact you! Thats the time i got, or switch from provider Openeprovider to x or switch from ISPconfig to x. Best option is a fix in ISPconfig for use of an other good Algoritm for DNSSEC.
