Are email addresses case sensitive?
But what does the standard says?
The RFC 5321, section 2.4 states: “The local-part of a mailbox MUST BE treated as case sensitive. […] Mailbox domains follow normal DNS rules and are hence not case sensitive.”
What does it mean? An email address format is composed of two parts local-part@domain. According to the standard, the local-part (i.e. the part before the “@”) should be case-sensitive. But in practice, all widely used email services have adopted the case insensitive format.
For all modern email services (e.g. Gmail, Outlook, Yahoo!, etc.), whether written in capitals, lowercase or mixed, the following email accounts are strictly identical:
In short, you are safe to treat email addresses as case-insensitive.