Adding an attachment in Gmail is really easy. If the file or document is on your Mac desktop, simply drag it to the Gmail compose window and Gmail will take care of the rest.
A quick drag and drop is all you need to do.
The problem is that not all the files are on the desktop. Some of your files may be located deep down in your Mac hard drive. And this is where Spotlight is useful — you can search these files by typing the file name in the Spotlight’s search box.
Drag and Drop Files As Attachment
If you want to attach a file, simply search in Spotlight and drag the file directly from Spotlight into your Gmail compose window. You don’t have to open any folder.
This is how you can quickly and easily attach files as attachment on Gmail. Given that I have 500GB of data and I am completely unorganized when it comes to organizing files, this little trick definitely makes my life a little more easier.
Related: Shipment Tracking Through Apple Mail.