Utilisation:
If ValidMail("toto@fai.fr") Then
     MsgBox "Adresse valide"
Else
     MsgBox "Adresse non correcte"
End if



Public Function ValidMail(ByVal mail_address As String) As Boolean 
    
    Dim rexp As RegExp

    'Nouvelle instance RegExp
    Set rexp = New RegExp

    'Ne fait pas la différence entre les majuscules/minuscules
    rexp.IgnoreCase = True
    'Donne seulement la première occurrence
    regEx.Global = False
    'Expression
    rexp.Pattern = "^[a-z0-9_.-]+@[a-z0-9.-]{2,}\.[a-z]{2,3}$"

    'Retourne le test
    ValidMail = rexp.Test(mail_address)
   
End Function

//Utilisation
string msg = ValidMail("toto@fai.fr") ? "Adresse valide" : "Adresse invalide";
MessageBox.Show(msg);



private bool ValidMail(string mail_address)
{
     Regex myRegex = new Regex(@"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$", RegexOptions.IgnoreCase);
     return myRegex.IsMatch(mail_address);
}

Utilisation:
If EmailValide("toto@fai.fr") Then
     MessageBox.Show("Adresse valide")
Else
     MessageBox.Show("Adresse invalide")
End if
 

 Private function EmailValide(ByVal mail_address As String) As Boolean
     Dim rexp as new Regex("^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$", RegexOptions.IgnoreCase)
     Return rexp.IsMatch(mail_address)
End Function

return preg_match('`^[[:alnum:]]([-_.]?[[:alnum:]])* 
@[[:alnum:]]([-.]?[[:alnum:]])*\.([a-z]{2,4})$`',$chaine); // renvoie true si le mail est valide, false sinon

function ValidMail(mail_address)
{
     return mail_address.match(/^([\w]+)@([\w]+)\.([\w]+)$/);
}
if ( ValidMail("toto@fai.fr") ) 
        alert("Adresse valide"); 
else  
        alert( "Adresse invalide");
</script>