Mail app updating offline disk cache
If your recipients use Mail, they receive the attachment as part of your message.
If they use another app or webmail, they receive a link to download the attachment. Attachments are available for 30 days and don’t count against your i Cloud storage.
To search in a specific mailbox, select a mailbox from the Mailboxes sidebar or the Favorites bar.
You can learn more about Mail from the built-in help included with your Mac.
Use the Attach button to add the attachment to your reply, then move your pointer over the image or PDF in your message.
Click the menu icon that appears in the upper-right corner of the attachment, then choose Markup from the menu that appears.
In OS X Yosemite or later, you can use the Markup feature to draw and type directly onto an attachment.If you're not ready to send your message, close its window or select another message.Mail keeps your unfinished messages in the Drafts mailbox.To change how your message looks: When you're finished, click Send .If you're offline, Mail keeps your outgoing messages in the Outbox mailbox until you connect to the Internet.