Explanation/Reference:
Explanation:
Retention Policy Tags are used to apply retention settings to folders and individual items such as e-mail messages. These settings specify how long a message remains in a mailbox and the action to be taken when the message reaches the specified retention age.
A Retention Policy is a group of retention tags that can be applied to a mailbox.
In this question, we have a new retention policy named Policy-90. We need to create a new retention tag to specify the deletion of email messages in the Deleted Items folder after 90 days. We then need to assign the retention tag to the Policy-90 retention policy. Then we apply the Policy-90 retention policy to mailboxes.
The New-RetentionPolicyTag cmdlet creates a new retention tag.
The Set-RetentionPolicy cmdlet adds the retention tag to the retention policy.
The Get-Mailbox cmdlet retrieves a list of mailboxes and the Set-Mailbox cmdlet is used to assign the retention policy to the mailboxes.
References:
https://technet.microsoft.com/en-GB/library/dd297955(v=exchg.150).aspx
https://technet.microsoft.com/en-GB/library/dd335226(v=exchg.150).aspx
https://technet.microsoft.com/en-us/library/dd335196(v=exchg.150).aspx