Unresponsive colleagues

I work as a GRC analyst. I help the company with ISO audits and vendor security assessments. Most of the time, I need to gather information from different stakeholders and business risk owners for evidence or simply a brief description how the vendor product works. But my emails and follow ups are often ignored. I'm chasing down people who clearly have better things to do but what can I do? How do you deal with them and their 10k+ emails …

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