Hi @pavan kumar ,
Microsoft 365 has a Recipient rate limit of 10000 recipients per day which cannot be customized. So agree with Robert that you would need to look for some third party solutions for your scenario. For more information about the sending limits in Exchange Online, hopefully you can find the official link shared above by Robert helpful.
By the way, if you found his post useful, it would be appreciated that you can accept his post as answer to close this up. This can make answer searching easier in this forum. If you have further concern on this, feel free to post back. Thanks!
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