Hello Praddyumna Shendurkar,
Based on my experience, after we sent emails through mail merge, since it uses Outlook desktop feature to send them, we need to recall messages in Outlook desktop client. However, there isn’t any option in Outlook to let end-user bulk recall messages. I totally understand that this feature is important for your work, and sincerely recommend you post a feedback in Outlook UserVoice. You can share your valued suggestion and idea with our related team, in the meantime, other members having the same demand can also vote for you. Your time and understanding will be greatly appreciated.
Thanks and Best Regards,
Anna