marketing mail automation with flow app

[Inma2024]

hello community!

the goal is to automatically send out a marketing mail.

therefore a separate landing page with a newsletter form with shopify forms was created that gives those customers a tag. after this a work flow with shopify flow app was created that sends out a marketing mail to those people, who subscribed via the landing page form and got the tag.

you'll find the work flow below. its working with some mails, but most mails get the error message (see below). 

Does anybody knows what we are doing wrong? 

[Ben310]

This is the German community and there's nothing in your spreadsheet: