Write and send email in Mail on iCloud.com
You can write and send emails on iCloud.com, save an email draft to send later, and change the default folder for sent email.
To send emails from a unique, random email address with iCloud+, see Use Hide My Email in Mail on iCloud.com.
Write and send email
In Mail on iCloud.com, tap
in the top right-hand corner of the window.A blank email opens.
Tip: To start an email from the iCloud.com homepage, tap
in the corner of the Mail tile. To start an email from anywhere on iCloud.com, tap 
in the toolbar, then tap Email Message.Type one or more names or email addresses in the address field. As you type, you see address suggestions.
To include Cc and Bcc address fields or select a different address to send from, tap Cc/Bcc or From.
Type your subject and your email.
You can format the text in your email by tapping
.To add an attachment, tap
.If your attachment is too big to send in an email, you can use Mail Drop. See Add an email attachment in Mail on iCloud.com.
Tap
in the top right-hand corner.
Undo a sent email
Tap Undo Send at the bottom of the screen to pull back the email.
Tip: By default, you have 10 seconds to change your mind, but you can change the amount of time. Tap 
at the top of the Mailboxes list, choose Settings, then choose Composing. Tap the pop-up menu next to Undo Send Delay and choose another option, or deselect it to turn it off.
Change the default folder for sent email
In Mail on iCloud.com, tap
at the top of the Mailboxes list, then choose Settings.Tap Mailbox Behaviour, select “Save sent messages in”, choose another folder or tap
to create a new folder, then tap Done.