Fix preferences for mail

The views use configs from constance that never existed, and furthermore now need to be defined and retrieved from dynamic-preferences.

changed milestone to %2.0a2

assigned to @yuha and unassigned @ZugBahnHof

created merge request !15 (merged) to address this issue

mentioned in merge request !15 (merged)

closed via commit c5a7a17d

mentioned in commit c5a7a17d

added part::backend part::frontend prio::2 labels