IF ELSE re exists: csv values

I have a csv input to a PowerShell script that has two email fields; the one that will always contain the value and the value that will sometimes be, and when the last value exists, the one I want to use to set the value used to set the mailcontact field later in the script to a variable $WriteEmail

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So, I have the following to read the CSV:

# Read contacts
ForEach ($contact in $contactfile) {

# Read attributes
$sourceEmail=$contact.Email
$sourceOutlookEmail=$contact.OutlookEmail

      

        
        
        
      

    

And I basically need this:

IF $sourceOutlookEmail IsNullOrWhitespace
THEN $WriteEmail=$sourceEmail
ELSE $WriteEmail=$sourceOutlookEmail

      

        
        
        
      

    

I just can't get the syntax right, I've tried all sorts of things. I know this is relatively simple, I just cannot get it to work.