The Computer Corner | San Miguel de Allende | Atención San Miguel
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The Computer Corner

By Charles Miller

In this column last week, I wrote the following: “Email addresses are not necessarily case sensitive. This means if your email address is, it is okay to write that address as or or if you care to do so.” This week I am going to explain that almost any statement defining the rules of the Internet could be continued with the words and or except or but.

A case in point is when I wrote, “Email addresses are not necessarily case sensitive.” I could have written “Email addresses are not necessarily case sensitive, but they could be.” The fact is that email addresses are very much case sensitive. Computers see uppercase letters and lowercase letters as being different (because they are different) and so and are, in fact, two different addresses. The network administrators in charge of the email server at could choose to make the email addresses in their domain case sensitive, but I am not aware of any email server on Earth that actually does this.

Making email addresses case sensitive would create massive confusion, interoperability problems, and other headaches. To require email addresses be typed with the correct case would be unwise because it would mean that maybe half of all emails would be returned for having the wrong address. This is why no email service I know of enforces case-sensitive email addresses. They all ignore the case altogether, treating both uppercase and lowercase as equals.

So even though it is permissible and technically possible for email addresses to be case sensitive because the standard says so, the de facto standard observed apparently by every email server on the Internet is that email addresses are all lower case and case-insensitive. This is a good thing because in some situations, you may discover that your computer makes it impossible to type email addresses using capital letters.

Earlier I wrote, “if your email address is it is okay to write that address as or or if you care to do so.” I could have added, “and even though those are technically different addresses they are treated as being the same.”

Sure, it is okay for you to write an email address like that, but just try typing in an email address like that and see what happens. Some email programs automatically change capital letters to lowercase. Try typing in somebody’s Gmail address as and do not be surprised if your computer automatically changes that to for you.

What this all means is that it is absolutely okay to print that address on your business cards as so it is easier to read. Case almost never matters in email addresses.

Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981, and now practically a full-time resident. He may be contacted at 044 415 101 8528 or email FAQ8 (at)


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