Congratulations on your new MacBook Pro! I understand how important is to have your email account setup on your new computer. I found a couple of resources that I think might help.
You can check the Mail Setup Assistant for the server settings for common email providers. I recommend checking your email settings here first to verify they match what you have in the Mail application:
If the Mail Setup Assistant does not provide settings for your email account, you can use the following article when contacting your email service provider to gather the necessary information to setup your account:
If you are able to setup your account but messages are not being downloaded, I recommend reviewing the following article:
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