DMARC disabled after editing
When editing DMARC record in DNS by Active is written "CHECKED" and there is not in a checkbox. (see attached screen). After saving the value DMARC record is de-activated. So there is need to go into DMARC record once again and click on un-checked checkbox.
Note: I don't know if it relevant but there was "ISPConfig – DKIM-Patch" installed before upgrading to 3.1.