Outlooker

Even though it may appear that Outlook should be able to send an email, there are occassionally issues, such as Outlook emails becoming caught in the outbox, that prevent this from occurring. Fortunately, you may resolve this issue on your own using the below-listed troubleshooting steps. For optimal results, complete each step one at a time until your problem is resolved or you've identified the most effective strategy.

Deactivate automatic updates

It is possible that you are not receiving emails from Outlook due to automated updates. Outlook may terminate unexpectedly when updates are installed, preventing email sending and receiving.

To prevent automatic updates, visit File > Options > Advanced. Remove the checkbox from the box beside Check for updates in the section titled Automatic Updates.

Source: https://sites.google.com/view/gethumanhelptech/blog/why-my-outlook-is-not-sending-emails