you need to check with your hosting support that default emails are not working.
if they are not providing default email support then you can use the below extensions
https://github.com/magepal/magento2-gmail-smtp-app
OR
https://github.com/mageplaza/magento-2-smtp
both are good. you just need to install and configure with any email service provider.
kindly Accept as a Solution if this works for you and give Kudos 