Find the retention period for your message tracking logs in Exchange 2010

Today I was faced with tracing an email from over 3 months ago.

I wasn't sure  if this was possible. So I checked the retention period for my message tracking logs.

Get-ExchangeServer | where {$_.isHubTransportServer -eq $true} | Get-TransportServer | select Name, *MessageTracking* | ft -AutoSize

Shortly I realize that I have 6 months worth of message logs however the fact that we only 

retain a certain amount of logs (10GB) of logs tells me that once this quota is met, I am no longer

 able to access 6 months of logs.