At my previous workplace we were hosting separate email servers for each customer on their own, private application instance. One of our clients was a national postal service from Europe, their corporate side forced them to use the highest notification frequency they could configure in our software upon all users.

After some time, their IT started reporting our IP address to various spam lists and they even sent abuse report to AWS. It was fun…

At least for me, I always made sure to never touch anything email-related, that’s how you become the “email guy”.

This has been going on for at least a decade, I’m not really sure how you can spend half a year and 20k doing something without stumbling upon countless examples of the same behaviour from Spamhaus & Co.

Sorry that this happened to you.