Fraud detection on hotmail from Simplenews Newsletter I send newsletters from my Drupal-7 website using Simplenews newsletter module.
But when a user has hotmail, the mail comes with a flag "Be careful. This sender is not approved by our controls for fraud detection."
I googled this and I saw that it has to do something with SPF but I don't understand what this is and what steps do I have to do to fix this issue.
Is there an option from administrator or a line of code I can use?
Thanks in advance!
There are a few steps you can also carry out by looking here How can I prevent my mail from being classified as spam?. It includes setting up Domain Keys, SPF etc.

You can also refer to some steps for Microsoft here How to prevent email sent from drupal from going into spam box.