If you have properly configured Magento 2 mailing systems, you may need to check below point:
Got to Stores -> Configuration -> Advanced -> System
Under Mail Sending Settings to make sure Disable Email Communications is set to No. Also, verify your Host and Port fields if you are using any external mailing server.
Got to Stores -> Configuration -> Sales -> Sales Emails
Under the General Settings tab, choose Asynchronous sending to Disable
Under Order tab Enabled to Yes
Now clear/refresh your cache also check-in log file. Another way setup cron or not check below command
php -dmemory_limit=-1 bin/magento cron:install
//cron run manually
php -dmemory_limit=-1 bin/magento cron:run
please more refer to this hope working link also useful.