Gmail IDs are case-sensitive

Is it okay to use capital letters in an email address?

[email protected] / [email protected]

Technically, these are different email addresses, but they are probably in Order.

The domain part of the email address ( is different not between Large and lower case. So "" is the same as "". Because the recipient (local part) may be case-sensitive, "hello" is different from "hello". However, real mail servers tend not to enforce this (I've never found one to do this) - as it is simply confusing and prone to user error.

If you save e-mail addresses, you should keep them in the original box (at least with the recipient) for security reasons. However, always compare them case-insensitive to avoid duplicates.

From RFC 2821 - Simple Mail Transfer Protocol:

The local part of a mailbox MUST be treated as case sensitive. Therefore, SMTP implementations MUST ensure that the case of local parts of the mailbox is preserved. Mailbox domains are not case-sensitive. For some hosts in particular, the "smith" user is different from the "Smith" user. However, capitalizing on local parts of the mailbox affects interoperability and is not recommended.