Change the Default Retention Policy in Exchange 2010 Hosted mode
List your available retention policies.

# Get-RetentionPolicy -Organization test.the.net.au

List your current Default Policy for the organisation.

# Get-MailboxPlan -Organization test.the.net.au | fl Ret*

There will be a Policy for each mailbox plan.

List your Policy for the mailbox.

# get-mailbox -organization test.the.net.au -Identity wes | fl Ret*

Change the Policy for a mailbox

# get-mailbox -organization test.the.net.au -Identity wes | Set-Mailbox -RetentionPolicy "test.the.net.au\Defau
lt Archive and Retention Policy"

Change the Policy for the organisation.

# Get-MailboxPlan -Organization test.the.net.au | Set-MailboxPlan -RetentionPolicy "test.the.net.au\DefaultRetentionPolicy"
# Start-OrganizationUpgrade test.the.net.au
# Complete-OrganizationUpgrade test.the.net.au