[pfooti]

Email RFC is weird. Did you know email addresses are supposed to be case sensitive? Like bob@ and Bob@ are two different addresses? Some services treat them this way, most don't. That intersection (oauth2 for example from Google can return [e-mail] if Bob has a GA4W account, which causes trouble when the oauth handler inconsistently lower-casifies input.

[rthille]

Really? By my reading RFC-5321 & RFC-5322 leaves interpretation of the local-part up to the software running on the host where the mail is delivered, but since that interpretation is up to those servers, intermediate servers must treat them as case sensitive and not make modifications to the local-part.

[FungalRaincloud]

That's my interpretation, as well. The standard is for carriers, not mailboxes. As a carrier, (or someone sending an email) you should respect case, as well as respect all of the special characters, because the server is allowed full decision power over whether those things are meaningfully used.