How should I write an email address? Are capitals OK?

[EC]

How should I write an email address? Are capitals OK?

An email address consists of:

username + @ + domain name

You can write an email address with CAPITAL LETTERS or with small letters, or with a mixture of the two. For example, [email protected] and [email protected] are the same.

Email addresses can contain:

• letters of the English alphabet
  numbers 0-9
  hyphens -
  underscore _
  dots .
  plus of course the mandatory at sign @

You cannot use spaces.

For example, all the following would be possible:
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]