I figured out the answer.
In exchange powershell ...
> $mbx = Get-Mailbox someUserName
> $mbx.EmailAddresses | where { $_.IsPrimaryAddress -eq "False" } | Export-CSV "C:\SomePath\wherever.csv"
> $mbx.EmailAddresses | where { $_.IsPrimaryAddress -eq "False" } | foreach { $mbx.EmailAddress -= $_.SmtpAddress }
> Set-Mailbox someUserName -EmailAddresses $mbx.EmailAddresses
> $mbx = Get-Mailbox theNewUser
> Import-CSV "C:\SomePath\wherever.csv" | foreach { $mbx.EmailAddresses += $._SmtpAddress }
> Set-Mailbox theNewUser -EmailAddresses $mbx.EmailAddresses
that's it :)
Of course, you might need to modify the contents of the csv file after the export and before the import.
I also had to delete all the existing email's from the someUserName
so there were no duplicates in theNewUser
good luck :)