Job changes can be detected by finding a change in the status of an email address that was previously verified.
There are multiple ways to test this, listed below in order of time/difficulty.
1. Email Verifications
Generate a list of people in your CRM that you know to have changed jobs
Use one of the many Email Verification apps to verify the list (see guide)
By doing this, you will be able to see the verification status and verification reason in the output.
2. CRM Verification/Monitoring:
Create a repeating scheduled CRM job for email verification (see quickstart guide). Be sure to the verification result in a CRM field on the Contact record.
Set up a CRM automation (eg: Salesforce Flow, Zapier, etc) that triggers on record update and compares the verification status. It should compare the previous verification status to the new one and detect a change. With this change detection, you can configure your automation to take the appropriate action (eg: send a warning email to the related account owner.