I'm currently working on an [mailtester](https://mailtester.ninja/) tool and need to implement syntax validation to ensure the email addresses are in the correct format. I'd like to know the best approaches for doing this in Python. Specifically, I'm interested in:

    Code examples using regular expressions or any built-in libraries.
    Handling edge cases and international email addresses.
    Any performance considerations or common pitfalls to avoid.

Any insights, best practices, or code snippets from those who have tackled this problem before would be greatly appreciated!