Case Sensitivity of an Email Address

 
This is a new blog.

There are two basic parts to
an email address. There's the
domain name and there's the other
part.

The domain name comes after the
@ sign and the other part comes
before the @ sign.

What are the two parts of an email?
There is the local part and
there is the domain name part.

Here's a Wikipedia Article that describes
this:

E-mail address

Today I could not remember whether or not the
local part of an email address is case sensitive.
Turns out the answer is not necessarily clear
cut.

According to the standard, the local part
of an email address should be case sensitive.

Because the local part is case sensitive,
all of the following email addresses should be
separate and distinct from each other. Each
is a unique email address. Each email
address could belong to a separate and
distinct person:

• ed@here.com
• Ed@here.com
• ED@here.com
• eD@here.com

What's the lesson? Sometimes
fine distinctions make a difference
and sometimes they do not.

In the case of the local part,
the distinctions made by changing
case do matter. In the case of
the domain name part, case distinctions
do not matter. Domain names are
case insensitive. That's according
to the standard.

It helps to know when to make a
more refined distinction and when
not to.

Here's another wrinkle. While the
standard says that the local part
of an email address is case sensitive,
common practice is that it is not case
sensitive.

Here's an article that presents both
sides of the issue:

Are Email Addresses Case Sensitive?

This is a case (pun unintentional) where
theory and practice differ.

Here's another important lesson: Don't
be too quick to believe standards established
by standards bodies.

I've had this experience over and over again.
I read a written standard and I believe it and
then I find out that the standard is not standard
practice.

Be careful to differentiate between a de facto
standard and a standard written by a standards
body. If there is a contradition, go with the
de facto standard.

In many cases, standards established by standards
bodies have never been implemented. In some cases,
they will never be implemented because they are so
wrong-headed.

Ed Abbott