Posted on the Google Apps Update Blog: 16 May 2013 05:50 PM PDT
Over the coming weeks, all Google Apps users get 30 GB of unified storage to use as you like between Drive and Gmail. This replaces the current replacing the current storage of 5 GB in Drive and 25 GB in Gmail. Just as before, files created in Docs, Sheets and Slides don’t count against your storage quota. Storage will also be shared with photos you upload to Google+ larger than 2048px. As a result of this change, Gmail inboxes are no longer limited to 25 GB – any additional storage can be shared and used by Gmail.
For more information, visit Bringing it all together for Google Apps customers: 30GB shared between Drive and Gmail