On the official Gmail blog, Phil Sharp, Gmail product manager, posted: “you can insert files from Drive directly into an email without leaving your Gmail.” He added, “…with Drive, you can insert files up to 10GB — 400 times larger than what you can send as a traditional attachment. Also, because you’re sending a file stored in the cloud, all your recipients will have access to the same, most-up-to-date version.”
In case all the recipients of the mail do not have access to the file in Google Drive, Gmail will prompt the user so the requisite settings can be altered from the open message box itself. Moreover, users also have the option of simply pasting the links of Google Drive files they want to share with the mail recipients in the compose box.
As of now, Google has only integrated Google Drive-based attachment feature in the new compose box. Therefore, users who had opted out of the new look of compose box need to opt for it once again in order to mail Google Drive-based files. Those who want to mail files bigger than 25MB in size need to transfer them to Google Drive in order to send them via Gmail.