Hello @supratim320,
I found a below page from Adobe that might be helpful for you:
Adobe Campaign Managed Cloud Services | Product Description

You mentioned you are sending big campaign and with no impact on performance.
There are below point you can consider for the performance .
1. Deliverability: When scaling up from your usual 1 million emails per day to 3 million for a big campaign, it's essential to be mindful of your IP reputation. While a temporary dip may occur, monitoring and managing your sender reputation should be a priority.
2. Performance: The performance of your campaign can vary based on delivery complexity. If you're incorporating personalization and complex calculations, expect that it might take more time compared to a simple delivery.
3. Contractual Limits: It would be good to check your contract with Adobe. This will help you understand any limits or guidelines for email sending under your current agreement. If you have any questions or need clarification, you can reach out to Adobe support or your Adobe success manager.
I hope you find this information helpful .
Kr,
Parvesh