Did capitals ever matter in email addresses?

email capitalization email-address
user588389 picture user588389 · Jan 26, 2012 · Viewed 40.9k times · Source

My dad says capitals used to matter (years ago) for email addresses but don't anymore. I'm fairly sure they never did because something like that involving DNS/MX changes would not change. Especially with no easy to find record online.

Answer

0x90 picture 0x90 · Jan 26, 2012

Let's look at this in pieces:

The domain part of the email address needs to conform to RFC 1034 and is thus (and has always been) case insensitive:

http://www.ietf.org/rfc/rfc1034.txt

The local part of the email address is handled by the receiving mail server and thus whether or not it is treated case-sensitively in theory depends on that server. Some mail servers choose to impose rules in addition to RFC 5322 (e.g. Gmail ignoring dots) or relax them (e.g. most mail servers in Asia allowing extended punctuation at beginnings and endings of addresses).

A mail server MAY in theory (while breaking RFC 5322) implement case sensitivity.

That said, I am not aware of a single one that does or has ever done so.

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