Microsoft 365’s spoof intelligence feature can be used to remove some errors and messaging in Outlook e.g. the “via sendgrid.net” or "via rp.mail.user-training.com" that appears after a sender email.

1. Go to the Microsoft 365 Security Portal

2. Navigate to Email & Collaboration > Policies & Rules > Threat Policies > Tenant Allow/Block List

3. Click on the Spoofing tab

4. Click Add

5. Configure the Add new domain pairs window

Paste the following into the Add domain pairs with wildcards field

Set Spoof Type to External

Set Action to Allow

6. Click Add to save your changes

Following the guide above will allow emails sent from usecure's IPs to spoof any sender domain. If you don’t feel comfortable using a wildcard in this allow list, you can add entries for each domain you wish to use for simulated phishing emails or system notifications.

For example: