Email Address Validation

Lot of peoples validate their field by using field length or Regular Expressions.

In this way, Email Addresses validation has been difficult some times.

Format of Email Address:
The format of email addresses is local-part@domain where the local-part may be up to 64 characters long and the domain name may have a maximum of 253 characters - but the maximum 256 characters length of a forward or reverse path restricts the entire email address to be no more than 254 characters.<sup id="cite_ref-0">[1]</sup> The formal definitions are in RFC 5322 (sections 3.2.3 and 3.4.1) and RFC 5321 - with a more readable form given in the informational RFC 3696<sup id="cite_ref-1">[2]</sup> and the associated errata.

Supported Characters:
The local-part of the email address may use any of these ASCII characters RFC 5322 Section 3.2.3:

• Uppercase and lowercase English letters (a–z, A–Z) (ASCII: 65-90, 97-122)
• Digits 0 to 9 (ASCII: 48-57)
• Characters !#$%&'*+-/=?^_`{|}~ (ASCII: 33, 35-39, 42, 43, 45, 47, 61, 63, 94-96, 123-126)
• Character . (dot, period, full stop) (ASCII: 46) provided that it is not the first or last character, and provided also that it does not appear two or more times consecutively (e.g. Kelvin..gm@example.com is not allowed.).
• Special characters are allowed with restrictions. They are:
• Space and "(),:;<>@[\] (ASCII: 32, 34, 40, 41, 44, 58, 59, 60, 62, 64, 91-93)
• The restrictions for special characters are that they must only be used when contained between quotation marks, and that 3 of them (The space, backslash \ and quotation mark " (ASCII: 32, 92, 34)) must also be preceded by a backslash \ (e.g. "\ \\\"").

Using in Android:

String email_Pattern = "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@"

+ "[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";

String email= mEmail.getText.toString();

if(email.matches(email_Pattern)){
System.out.println("Valid Email Address");
} else {
System.out.println("Invalid Email Address");
}

Also you can try in TextWatcher interfaces.