I think i figured out part of the problem. In the CLI, mailgun returns domain not found if I use https://api.mailgun.net/v3/mg.brunoamaral.net/messages
But if works with api.eu.mailgun.net. Is that previous API domain hardcoded?
The “Split in Batches”-Node is meant if you have a lot of items and you want to iterate only on a smaller amount of them at once. Like for example in this example:
There it is possible that thousands of URLs get read from the Spreadsheet but sending thousands of URLs to one API would simply produce thousands of errors. So with the help of that node, they can be split in smaller batches and the data so processed step by step.