iCloud: Add an email attachment in iCloud Mail
You can attach one or more files to a message when you use Mail on iCloud.com.
If you want to attach files that are too large to send in email, you can use Mail Drop. It lets you upload attachments up to 5 GB and send a link or preview to your recipients. You can send these attachments from iCloud.com or from the Mail app on your iOS device (iOS 9.2 or later) or Mac (OS X 10.11 or later).
Recipients can download Mail Drop attachments for 30 days after they’re sent.
Add an attachment
While writing a new message, click the Attach button at the top of the message window.
Select the files you want to attach, then click the Choose or Open button to begin uploading the files.
If your attachments are too large to send in email, you’re asked if you want to deliver the attachments using Mail Drop. If you agree and Mail Drop is turned on, the attachments are uploaded to iCloud.
It may take some time for the upload to complete, depending on the size of the files.
To attach more files, repeat steps 1 and 2.
You can also simply drag files into your message. If you use Internet Explorer 9, drag and drop requires an add-on and Mail Drop isn’t supported. See the Apple Support article About iCloud add-ons, extensions, and plug-ins for Windows browsers.
Remove an attachment
In the Mail Message window, click the Remove icon next to the attachment’s filename.
You can only remove an attachment before you send the message.
Turn on Mail Drop for large attachments
If you want to use Mail Drop to deliver large attachments, make sure it’s selected in iCloud Mail preferences.
Click the Action pop-up menu in the sidebar, then choose Preferences.
Click Composing, then select “Use Mail Drop when sending large attachments.”
For information about including original attachments in a reply, see Reply to or forward email in iCloud Mail.
You can’t remove files already sent with Mail Drop. They expire after 30 days.
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 messages, or using compression software, such as the Compress feature on a Mac, to make your attachments as small as possible.