Hi @Marie_Widmer and welcome to the Asana Community Forum!
For security reasons, only members of your Organisation/Workspace can create task in Asana. So when emailing a task into Asana, our system systematically checks the sender’s email address and will automatically reject the email if the sender isn’t a member of your Organisation/Workspace. You can learn more about this in the following article: https://asana.com/guide/help/email/email-to-asana (refer to the “Asana tips”).
Depending on your set up you could either:
- Create a List of contact including all members of your organization in Gmail, and then set your rules in Gmail to redirect to Asana only email coming from this list.
- Systematically invite these users as Guest of your Organisation.
Hope this helps!