How can I use PowerShell to add emails to user's Safe Sender list?

Before proceeding with this guide, ensure you have gone through the complete requirements in this article:
https://support.holmsecurity.com/knowledge/how-do-i-whitelist-a-domain-in-office-365

This PowerShell method goes through every mailbox in your Microsoft 365 tenant and adds several specific email addresses to each user’s Safe Senders list. 

Version-Safe Script

Description of what the script does for you:

• Detects whether you’re connected to Exchange Online or on-prem.

• Adds your trusted simulation sender addresses only if not already present.

• Remember to edit and change the $trustedSenders to the adresses of the domain category you plan to use.

Download here: Add_trusted_sender_VersionSafe.ps1

Compatibility Overview