Google Vault

Vault is entirely web-based, so there's no need to install or maintain any software. 

Vault licenses costs an additional $5 + VAT per user, per month.

Note:  Vault is included with the G Suite Enterprise or Business or Education edition.

Add archiving and e-discovery to Google Apps

Retention policies: Define retention policies that are automatically applied to your email and chat messages.

Email and chat archiving: Your email and chat messages are archived and retained according to your policies, preventing inadvertent deletions.

E-discovery: Be prepared for litigation and compliance audits with powerful search tools that help you find and retrieve relevant email and chat messages.

Legal hold: Place legal holds on users as needed. Email and chat messages can’t be deleted by users when they’re placed on hold.

Export: Export specific email and chat messages to standard formats for additional processing and review.

Audits: Run reports on user activity and actions in the archive. Searches, message views, exports and more are shown.