Instead of sending file attachments in your e-mail, store the file in a SharePoint library and send a link instead.
Go into the SharePoint library that has the file and select the checkbox next to the file name. Then navigate to Library Tools > Library, and click the E-mail a Link option in the Ribbon Bar:
Because of the integration with Microsoft Outlook, it instantly opens up an e-mail with the link in the body. It’s ready for you to start composing your message:
Only users with permission to the SharePoint library will be able to open the file when clicking on the link. This method ensures users always see the most current version of the file, and it reduces the amount of space that gets added to your e-mail file when sending file attachments.