I used the Web Developer plugin and https://github.com/JElchison/curl-auth-csrf to investigate the dropscan.de REST API a little:
curl-auth-csrf.py -i https://secure.dropscan.de/login -f form-login -d "user[email]=$EMAIL" -p "user[password]" $URL
URL=https://secure.dropscan.de/scanboxes/[ID?]/mailings.json?filter=received&sort=created_at
[
{
"barcode": "C00123456",