Recover deleted Google Apps email messages
When a user clicks Delete, the Google Apps email message moves to the Trash, but it remains available to the user for 30 days. If it has been fewer than 30 days and the message hasn't been permanently deleted, the user can follow the steps in Recover deleted messages.
Restore a user's Google Drive or Gmail data from the Admin Console
You can restore deleted Google Drive files or Gmail messages for one or more users for a date range you specify. This helps ensure that, if a user accidentally deletes important data, that data is not permanently lost. Learn more.
Recovering Deleted Messages with the Email Audit API
If you can't find your messages in All Mail, Spam, or Trash, or by performing a search, then they've been permanently removed from Gmail, possibly deleted by someone else. We regret that we are unable to recover messages that have been permanently deleted. If you're concerned that someone may have gained access to your address, we suggest that you take the following measures to protect your account.
Also, please check with your domain administrator to see if two-step verification is available for your domain. Please consult our overview on two-step verification for Google Apps accounts.
Google Apps Vault
With Google Apps Vault, you can safely preserve email and on-the-record chats in Google's highly secure data centers. Apply retention rules to comply with your organization's policies and apply message holds to preserve specific emails and chat sessions when required.
For non-email data recovery solutions, please consult the Google Apps Marketplace, where one of our partners may have a solution suitable for your needs.