Gmail users facing full inbox storage can resolve the issue by managing their 15GB of free space shared with Google Drive and Photos. Large attachments, old emails, and promotional messages consume significant storage. Users can find and delete these by searching for emails larger than a specific size (e.g., size:10M) or older than a certain period (e.g., older_than:2y). Emptying the Trash folder is crucial to reclaim space. Deleting promotional and social emails can also free up considerable storage.