How do I delete hundreds of emails from my mailbox?

Top left of your Mail screen there is a left arrow. Click and it should show your mailboxes. Below are a greyrsion of the mailboxes. Click the down arrow on the mailbox you have junk mail in. It will open to show all your mailboxes for that account, inbox, sent, drafts and junk. Open junk and click edit. Each junk mail item will show a circle to the left. Click the circle and it is ticked. Click delete. Also you can delete the lot by clicking delete all, bottom right. Good luck.

Is your email account type POP3 or IMAP ?

If it is a POP3 account, this problem (used space) may not go away. I have the same problem with my iPhone 7 and had it with my iPhone 5.

Try deleting your POP3 email account, and then create an IMAP email account.

Hi Susan,

I have taken the sentence below from an Apple Help page.
I hope this finds you well,
Niall

Go into Settings > Mail, Contacts & Calendars, select the account you don't want, and then choose to delete it.

Not all tablets are the same, but if this is email you are talking about, you need to check all drop down menus to find the "Clear Mailbox" option.
I guess you have tried doing a Google search on the brand name and model number as shown on the Tablet ? If not... try that.
Also, read the User manual which should be available as free download from the manufacturer's website.
If you have a "unknown brand" product, and cannot find the website for it you can always try taking a look on gumtree.com for someone who is advertising one like yours to sell, as they may have the manual and be happy to tell you how.

Enter the email address you'd like to create in the "Email Address" field. You may also enter a display name in the "Name" field. Then click the Next button.

Enter the email address you'd like to create in the "Email Address" field. You may also enter a display name in the "Name" field. Then click the Next button.

If you will use only POP (Post Office Protocol) to access this new email, you can select the second option; you won't need a Yahoo ID to activate the address.
On the invitation page, enter the email address to send the invitation to.
Be sure to assign mailboxes at your domain only to people you trust. Yahoo maintains a strict policy against spam and abuse and will suspend domain names that are associated with these types of behavior.
You are responsible for actions taken by anyone using an email address associated with your domain. If anyone using your domain is found to have violated the Yahoo Terms of Service in conjunction with a Business Mail plan, Yahoo reserves the right to suspend the domain and deactivate any mailboxes associated with it.

Settings/Mail, Contacts, Calendars then tap the account you're having trouble with.

Assuming you're using an IMAP account, tap the account user ID on the first line. Scroll to the bottom and tap Advanced.

Tap Deleted Mailbox. In the ON THE SERVER section, tap Trash (making the Trash mailbox on the server your "Trash" location). Back up to Advanced and make sure MOVE DISCARDED MESSAGES INTO: is set to Deleted Mailbox.

You may want to do the same thing for your Sent Mailbox (using Sent on the server for sent messages - so they're retrievable from your desktop).

This fix may result in all the old deleted messages on the iPad being moved to the server and then showing up again in your deleted messages on your desktop. The Mail app will eventually delete them as it does any deleted messages according to its settings.

Look for the Accounts section below your mailboxes (see image)

Select the account that you want to delete emails from. Select the folder (for example -Trash) Tap on this folder, and you will see the word "Edit" at the top right. Tap on Edit, select the emails that you want to delete (a blue check mark will appear to the left of each selection), and then look for the word "Delete" at the bottom right of the list of emails that you have selected. Tap on Delete and that should solve your problem.

Dear Thomas,
There is an easy way to empty the trash folder on your iPad email app. Here is how:
1. Open the "Mail" app on your iPad.
2. Tap on the upper-left icon in the Mail app. It might say, "Mailboxes" or in my case, it says "Gmail".

3. Tap on the email account you are using. Mine says, "Gmail", yours might say, "Yahoo" or whatever program you are using.
4. Tap on the "Trash" folder for your email account.
5. Now that you are looking at the items in the trash folder, tap on the "Edit" button located just to the right of the word, "Trash".
6. Tap on the "Delete All" icon at the bottom of the screen.
7. A larger "Delete All" button will appear. Tap on that as well.
8. In a few seconds (or longer if you have lots of messages in the deleted folder) all your messages will be gone and the "Trash" folder will be empty.

Check the email address, correct as needed.