What leads to automatic capitalization of the username (email) in GCP IAM?

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Automatic capitalization of the username (email) in GCP IAM may occur due to the following reasons:

1. The first letter of the username (email) is always capitalized.
2. GCP IAM recognizes certain email providers like Gmail, Yahoo, etc., and automatically capitalizes the domain name part of the email address.
3. Some web browsers automatically capitalize the first letter of the email address when it is entered. This can be disabled or changed in the browser settings.