Dear Harshal Parikh
Thank you for your reply.
I understand there are concerns about the security of your account. There are settings that can increase the security of your account, but first you will need to log in to your Microsoft account before you can take the next step.
If you have access to your account
As the intruder already knows the full name of your account, I would recommend that you disable access to your current account name to stop the intruder from logging in repeatedly.
You need to click on this link first( https://account.microsoft.com/)
Log in to your Microsoft account and click [Your Information] on the left, then [Edit Account Information] on the right side of the screen that opens. From this screen, you can add an alias as a new login name for your account. Due to the current security risks associated with your account, I recommend that you create an alias with the outlook.com extension that does not require authentication. (If you are using the custom alias below, you will be prompted to verify that this alias exists. Only actual mailboxes can be added as aliases.
Then, you need to click [Set as primary alias] to the right of the new alias to make it the primary alias. After that, click [Change Login Privileges] at the bottom and remove the tick mark in front of the current account name. You have successfully removed the login privileges of the account name. You can test this by typing your account name into the login screen and Microsoft will prevent you from logging in by prompting you with the message "This username is closed and cannot be used to log in". Intruders will receive the same message when trying to log in using this name.. Please note that in this case you will not be able to log in using this account name. Please remember the account name you changed. Additionally, we have tested that you can still send and receive emails using this account name and that the sender can use your account name as the recipient of the email and that email functionality is not affected.
After modifying the login privileges of your account name, I suggest you also use the [Logout from all locations] feature, which will log out your account's login status in all locations, and the intruder will not be able to try to access your account without knowing the current name of your account.
If you are currently unable to access your account
You may not be able to protect your account using the methods described above. As you can change your account password, your account does not need to be recovered in a similar way to resetting your password, most account recovery methods will not work in your current situation, I can only recommend that you seek further advice from Microsoft online support to recover your access to your account.
You will need to click on this link and follow the instructions below to find them.
1.First enter your question into the search(input“MSA”), then click "Sign in to contact support" at the bottom of the page.
2. Currently logged in to another valid Micorsoft account.
- Under "Microsoft 365 and Office", select "manage account security".

- Under Categories, select Manage Account Security, and then click Confirm.
- Click Chat with Support Agent in Web Browser.
I wish you all the best
Carmid.L-MSFT | Microsoft Community Support Specialist