Concerns about Outlook security

After discovering that my Outlook account had been hacked, I changed my password and verification settings, on July 27.  Since that time I have received more than 30 messages from the Microsoft Account Team including a "Single Use Code" for sign-on.  All of these represent sign-on attempts made by someone other than myself.  

The message from the Account Team says "If you didn't request this code, you can safely ignore this email. Someone else might have typed your email address by mistake." Nonetheless, this seems like a relentless campaign to get into my account, perhaps by some sort of bot.  What should I do?