To get a list of SMTP addresses and export to CSV:

 

 

Get-Mailbox -ResultSize Unlimited |Select-Object DisplayName,PrimarySmtpAddress, @{Name=“EmailAddresses”;Expression={$_.EmailAddresses |Where-Object {$_.PrefixString -ceq “smtp”} | ForEach-Object {$_.SmtpAddress}}} | Export-CSV "C:\Temp\List-SMTP-Address.csv"