@Nagashree Balasundaram Thank you for reaching out to Microsoft Q&A. Sorry for the delay in response. Unfortunately, we cannot customize admin emails like "New subscription notification" and currently, only the email going out to the users can be customized.
We do have feature request [https://feedback.azure.com/d365community/idea/7a5df961-0025-ec11-b6e6-000d3a4f0858 for this and would recommend you upvote it (I upvoted :)). This will really help our product team review and prioritize the features accordingly. Also, I have shared your feedback directly with our product team internally on the same.
I hope this answers your question and feel free to add a comment if you have any other questions. We would be happy to assist you. Please 'Accept as answer' if it helped so that it can help others in the community.