Hi @hyenokian
Thanks for your reply.
1. We have a lot of surveys and the problem appears on all the surveys. Here you got a link of one of the surveys: https://matchtool.nl/vragenlijst-magazijnmedewerker-nieuwegein/
2. Yes, we have a caching plugin, I have cleared all the caches. But we still have the same problem.
3. Yes, its an ordinary email thats sent from our webpage.
4. No we don’t have an SMTP plugin activated.