outlook is not sending mails with my icloud account

Hi,

When i send an email from my outlook app using my icloud account I get the following error

Technical details

SmtpSubmissionPermanent5XXException: Smtp submission failed. Server 'smtp.mail.me.com' Port '587'. --> Unexpected SMTP server response. Expected: 250, actual: 550, whole response: 550 5.7.1 message content rejected
 

This happens on my iphone and on my macbook.

I already tried deleting the accounts in outlook and reset them also recreated the appspecific password.

Sending emails from the normal apple mail app works fine and is now my work arround, but of course this is not the ideal way of working.

Any help, ideas,... are welcome