fix #2228: automatically deliver/delete on whitelist/blacklist

fix #2228: automatically deliver/delete on whitelist/blacklist

If a user chooses to blacklist a specific sender of a mail, the mail
is highly probably undesired too, so delete it in that case.

The reverse should hold for white listing a mail's sender, deliver it
in that case.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Tested-By: Stoiko Ivanov <s.ivanov@proxmox.com>
Reviewed-By: Stoiko Ivanov <s.ivanov@proxmox.com>