Get a list of addresses, c:\export to smtp.csv
Get-Mailbox -ResultSize Unlimited |Select-Object DisplayName,ServerName,PrimarySmtpAddress, @{Name=“EmailAddresses”;Expression={$_.EmailAddresses |Where-Object {$_.PrefixString -ceq “smtp”} | ForEach-Object {$_.SmtpAddress}}} | Export-CSV c:\smtp.csv -NoTypeInformation