Can't send e-mails from my hotmail-account. Yet receiving is no problem

Can’t send emails with my hotmail address. Yet receiving emails sent to my hotmail address is not a problem …
When I try to send an email, they are then shown in the “out” folder.

Do you use the native hotmail app or the mail app form the OS ?
Do you have advanced privacy with tracker blocker enabled ?
It may be in some case the origin of your problem.
You have to desactivate the blocking of one tracker related to hotmail.