function emailCheck (emailStr) {
    var checkTLD=1;
    var knownDomsPat=/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum)$/;
    var emailPat=/^(.+)@(.+)$/;
    var specialChars="\\(\\)><@,;:\\\\\\\"\\.\\[\\]";
    var validChars="\[^\\s" + specialChars + "\]";
    var quotedUser="(\"[^\"]*\")";
    var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;
    var atom=validChars + '+';
    var word="(" + atom + "|" + quotedUser + ")";
    var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
    var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");
    var matchArray=emailStr.match(emailPat);
    if (matchArray==null) {
    alert("Your e-mail adress is missing or incorrect (check @ and .'s)");
    return false;
    }
    var user=matchArray[1];
    var domain=matchArray[2];
    for (i=0; i<user.length; i++) {
    if (user.charCodeAt(i)>127) {
    alert("Your e-mail adress has invalid characters.");
    return false;
       }
    }
    for (i=0; i<domain.length; i++) {
    if (domain.charCodeAt(i)>127) {
    alert("The domain of the e-mail adress has invalid characters.");
    return false;
       }
    }
    if (user.match(userPat)==null) {
    alert("The e-mail adress seems incorrect, please check.");
    return false;
    }
    var IPArray=domain.match(ipDomainPat);
    if (IPArray!=null) {
    for (var i=1;i<=4;i++) {
    if (IPArray[i]>255) {
    alert("The destination IP adress is incorrect!");
    return false;
       }
    }
    return true;
    }
    var atomPat=new RegExp("^" + atom + "$");
    var domArr=domain.split(".");
    var len=domArr.length;
    for (i=0;i<len;i++) {
    if (domArr[i].search(atomPat)==-1) {
    alert("The e-mail adress seems incorrect, please check possible typing errors.");
    return false;
       }
    }
    if (checkTLD && domArr[domArr.length-1].length!=2 && 
    domArr[domArr.length-1].search(knownDomsPat)==-1) {
    alert("Your e/mail adress should end in a domain.");
    return false;
    }
    if (len<2) {
    alert("The host adress in your e-mail is missing, please check. Or you typed a blank space at the end of your adress, please correct the mistake and try again.");
    return false;
    }
    return true;
    }