Block changing your email address in the administration to members.thalia.nu

One-sentence description

Block changing your email address in the administration to members.thalia.nu

Current behaviour / Reproducing the bug

Users can change their email address to members.thalia.nu.

Expected behaviour

No changing to addresses using this domain. Since we do not want these addresses in the administration. We cannot rely on them to stay active.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information