cleaning up Mailboxes (Delete emails older than 30 days and X size)

We have a requirement of cleaning up Mailboxes (Delete emails older than 30 days and X size) for some employees. Does MS exchange 2010 has any native support for this ? we are planning to do this for 2000 mailboxes on a daily basis based on a condition older than 30 days. Can some one please guide on how to do this ? If RetentionPolicyTag is the only option, How
efficient it is to implement this for 2000 users ? Can you please suggest us the best practice ?

Thanks in advance