Compose a New Mail Message with an Attachment by Drag & Drop
Surely everyone knows by now that you can drag and drop files directly into Mail messages to attach those files to an email, but did you know you can instantly create a new email with an attachment by dragging the file in question to Mail’s Dock icon instead?
Try it out, drag any file directly into the Mail icon. You’ll immediately have a new blank email message with that file attached.
Sometimes the simplest tips are the best, and despite using OS X and Mail app since 10.0 I’ve never known that just dragging and dropping a file into the Dock icon automatically creates a new Mail message with that file as an attachment. Amazingly useful but simple tip found on MacGasm, though it doesn’t require the Command key as they suggest.