In case you don't know your way around your Galaxy S10 Email app and menus, then you can check the info below and learn how to remove emails easily.
If you are not using the Gmail and you are using the Samsung Email app in order to manage your email accounts. The Samsung Email is capable of managing all your email addresses and if you are first time using this app to do it, then you can learn how to use it using the info below.
Samsung Email app features support for Gmail, Yahoo Mail, Hotmail Outlook, Exchange, Office365 and Other email services you are currently using.
How to delete email messages on Samsung Galaxy S10:
Open the Samsung Email app, and then open your email account. Go to the More settings option and open these. Use the Edit option.
Now you can select all the email messages that you wish to remove. When you are done removing the emails you can simply close the Samsung Email app and you are done.
If you want to remove all the email messages in your Inbox, then you should select the "all" option and the Samsung device will select all the email messages in your inbox. After that you need to tap the "delete" option to remove all of them.
If you need any extra help managing other Samsung settings and options, then you should tell us in comments and we will try to come up with a solution.
Please note that in case you cannot open or use the Samsung Email app, then you will need to try and clear all of its data in order to make it work again. Go to Settings> Apps> Samsung Email> Storage and use the "clear data". This will restore the app to its original state and you will have to restart the app setup in order o make it work as before.