Delete email in Mail on iCloud.com
Deleted emails are moved to the Bin mailbox. When you delete an email, it is saved in your Bin for 30 days, after which it is permanently erased. When you delete an email from iCloud.com, it is deleted on all your devices that have Mail turned on in iCloud settings.
You can also change where your deleted emails are stored.
Important: If you view iCloud Mail in another app (for example, the Mail app on your iPhone or iPad), your mail might be deleted sooner than 30 days depending on the app’s settings.
Delete emails
Go to icloud.com/mail, then sign in to your Apple Account (if necessary).
Select the email or emails you want to delete.
Tip: To select all emails in a folder, press Command-A on a Mac (or Control-A on a Windows device).
Do either of the following:
If you selected one email: Click
at the top right-hand corner.If you selected multiple emails: Click Bin.
If you see 
or Archive, you have “Show Archive icon in the toolbar” selected in Mail settings. See Archive email in Mail on iCloud.com. To delete an email or emails, do one of the following:
If you selected one email: Click
at the top right-hand corner then click Bin Message.If you selected multiple emails: Click Move, click Bin, then click Move.
Tip: You can also hold your pointer over an email in the message list, click 
then choose Bin Message.
Empty the Bin
You can delete all the emails in the Bin at the same time.
Important: When you empty the Bin, the emails are permanently deleted. You cannot recover them.
Go to icloud.com/mail, then sign in to your (if necessary).Apple Account
Click
at the top of the Mailboxes list.Choose Empty Bin, then click Empty Bin again.
Erase emails immediately and permanently
You can set iCloud Mail to permanently and immediately erase emails when you delete them, instead of moving them to the Bin.
Go to icloud.com/mail, then sign in to your (if necessary).Apple Account
Click
at the top of the Mailboxes list, then choose Settings.Click Mailbox Behaviour, then deselect “Move deleted messages to”.
Change the location of deleted emails
By default, emails in iCloud Mail are moved to the Bin when you delete them. You can change the folder they are moved to.
Go to icloud.com/mail, then sign in to your (if necessary).Apple Account
Click
at the top of the Mailboxes list, then choose Settings.Click Mailbox Behaviour, select “Move deleted messages to”, then click the current folder.
Choose another folder or click
to create a new folder, then click Done.
To delete Mail folders, see Organise email with folders in Mail on iCloud.com.