For anyone who thinks that may be a hand wave, there isn't a standard way to normalize email addresses. If you're building to the spec, then the local part can be processed case-sensitively, so Django lowercases the part after @ only. Others strip out stuff like gmail's +tags and really get into the weeds of how different email providers process emails.

https://pypi.org/project/email-normalize/

https://stackoverflow.com/questions/9807909/are-email-addres...