When you have external legitimate email sender’s email address and domains, it may have been end up in Junk E-Mail in Outlook. You can tell users to right click on the email in Junk E-Mail folder and select Junk –> Never Block Sender (or Never Block Sender’s Domain). But every user had to do this by him/herself.
I wrote a script to add Safe Sender’s email and domain from a text file to all Mailboxes in the Exchange. This is based on Set-MailboxJunkEmailConfiguration Exchange cmdlet. You can download this script and run it as it is. All you need is a text file with emails & domains in separate line on the same location of script file.
Download the script SetSafeSendersList.ps1. Enjoy.