Are email addresses case sensitive?

Question

I\'ve read that by standard first part of e-mail is case sensitive, however I\'ve tried to send e-mail to name@example.com, Name@example.com and

Answer 1

IETF Open Standards RFC 5321 2.4. General Syntax Principles and Transaction Model

SMTP implementations MUST take care to preserve the case of mailbox local-parts. In particular, for some hosts, the user "smith" is different from the user "Smith".

Mailbox domains follow normal DNS rules and are hence not case sensitive