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"