i just gave it a run and it worked great. i just added the -confirm:$false so i do not have to answer the prompts to confirm each user mailbox export.
Get-Mailbox -Database “ftlx5\Fourth Storage Group\Mailbox Database 3″ |
Foreach-Object {
Export-Mailbox $_.Identity -PSTfolderpath “Y:\FOSG-MD3\$($_.PrimarySmtpAddress).pst” -confirm:$false
}