Get every object and property:

Get-ADUser -Filter * -Properties *| select * | Export-CSV "C:\PS_Every_Object.csv"

^ Depending on the number of user this could take a few minutes to run. This is also handy to hunt for properties.

This will export userId, email, employee Id, and company name.

Get-ADUser -Filter * -Properties SamAccountName,EmailAddress,EmployeeID,Company | select SamAccountName,EmailAddress,EmployeeID,Company | Export-CSV "C:\Email_Addresses.csv"