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Does Capitalization Matter In Email Addresses

I’m sure it has crossed your mind when you accidentally leave the Caps Lock on. And while you quickly fix what you think is a mistake, you can’t help but wonder…

Does Capitalization Matter In Email Addresses?

In this post, we set out to discover what the web has to say and give you the most detailed answer.

Let’s end the debate once and for all so you can go ahead and focus on more important tasks.

So, does capitalization matter in email addresses?

Short answer: No!

An email address can start with a capital letter or include capitals anywhere in the address. If you happen to capitalize your email address, or your autocorrect simply messes up, fear not.

You will be fine!

Unlike passwords, email addresses are not case sensitive.

Whether or not you add capitals, your email server will read it the same way as long as the numbers and letters match your official email address.

The examples below all form the same email address and end up in the same inbox because they all form the same letters and numbers.



Why Does This Happen?

An email address is a combination of two different parts:

  • The part after the @ symbol represents your email server and tells the web to send your email there.
  • Everything before the @ symbol informs that server about the owner of the mailbox.

1. Capitalizing the domain name

The text that follows the @ symbol is called “domain name” and is case insensitive in email addresses, the same way as everywhere else on the internet.

What this means, is that there is no difference between and WWW.GMAIL.COM.

When it comes to File Transfer Protocols (FTP), the same thing applies. This is why there is no difference when sending your emails with or without capitals. You can choose to send an email to:



  • youraddress@MAILIGEN.COM

And the result will be the same.

For this reason, capitalization in an email address’s domain part does not affect its deliverability in any way.

2. Capitalizing the unique address

For the first part of your address, things can become more complicated. Over the years, there have been many revisions to the email protocol (RFC – a set of rules that everyone must follow and respect for interoperability).

The latest core version is RFC 5322 but that is supplemented by many other protocols such as RFC 6854.

On top of that, there is a protocol which explains how email is forwarded (it can be found under the name SMTP* panel in your email software preferences).

*=Simple Mail Transfer Protocol

It’s also important to note that in the latest version of RFC 5336 it is mentioned that the first part of the address may be case sensitive. On the contrary, the previous version of the same SMTP states that the first part of an address is case insensitive.

For that reason, theoretically speaking, there may be some servers that contain two separate mailboxes that essentially have the same email address, only with a different form of capitalization:




If such cases exist, they are very rare and outdated. Gmail, as well as Postfix, which is more common with Linux users, are both case insensitive.

Summing up

If we can give one fast and easy answer to the question “Does capitalization matter in Email addresses?” the answer would be No.

That’s all folks!

We hope you found this guide useful. Let us know if you have any questions and we will make sure to help you out.

Does Capitalization Matter In Email Addresses
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    June 9, 2019 at 5:29 pm

    Thanks for this all!
    Actually Email capitalization does not matter in EMAIL but does matter in Usernames while choosing on various account creation sites.

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