iCloud: Send email using an alias
You can set up iCloud Mail to send messages from an alias email address.
For example, you can use your main iCloud Mail address with friends and family only, and use an email alias for online registrations and purchases, joining mailing lists, and so on. This makes it easier to monitor the sources of unwanted messages.
Click the Compose button.
Type one or more names or email addresses in an address field. If addresses don’t appear enclosed in blue fields, separate them with commas.
As you type, iCloud Mail tries to suggest a complete address. To use it, press Return.
If a list of suggestions appears, click one to use it. Suggestions include matching addresses from iCloud Contacts, recipients you recently emailed, and groups of recipients you emailed together at least twice recently.
To remove a recent recipient or group of recent recipients from the list, move the pointer over the recent recipient or recipient group you want to remove, then click the Remove button next to the recipient name or names.
To view all of your contacts, click the Add button at the right end of the address field.
To include Cc and Bcc address fields, click Cc/Bcc.
In the Subject field, type a subject for the email.
Click the From pop-up menu, then choose an alias email address.
This is the address that the recipient will see.
Type your message, then click Send in the upper-right corner of the iCloud Mail window.
You can also use OS X Mail to send messages using an alias. When composing a message, click the From pop-up menu, then choose the alias.
Note: If you send an email with large attachments, it might be returned by the recipient’s email service because your email exceeds the size limit set by that email service. You can try sending the contents of your message in multiple email messages, or using compression software, such as the Compress feature on a Mac, to make your attachments as small as possible.