As part of OS X Yosemite, Apple has updated the Mail experience. In addition to the visual update, Mail has some major new feature, particularly MailDrop and Markup.
MailDrop is a way of sending large attachments through email. Attachments up to 5GB can be encyrpted and routed to contacts. Secure links will be created when a file is too large to be sent to a recipient directly. Markup allows you to draw right in emails. Arrows and other shapes will be recognized. Mail now includes a magnifying glass "loupe" zoom. You can also sign using the trackpad.
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