function emailCheck(emailStr) 
{
    /* The following variable tells the rest of the function whether or not
       to verify that the address ends in a two-letter country or well-known
       TLD.  1 means check it, 0 means don't. */

    var checkTLD=1;

    /* The following is the list of known TLDs that an e-mail address must end with. */

    var knownDomsPat=/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum)$/;

    /* The following pattern is used to check if the entered e-mail address
       fits the user@domain format.  It also is used to separate the username
       from the domain. */

    var emailPat=/^(.+)@(.+)$/;

    /* The following string represents the pattern for matching all special
       characters.  We don't want to allow special characters in the address. 
       These characters include ( ) < > @ , ; : \ " . [ ] */

    var specialChars="\\(\\)><@,;:\\\\\\\"\\.\\[\\]";

    /* The following string represents the range of characters allowed in a 
       username or domainname.  It really states which chars aren't allowed.*/

    var validChars="\[^\\s" + specialChars + "\]";

    /* The following pattern applies if the "user" is a quoted string (in
       which case, there are no rules about which characters are allowed
       and which aren't; anything goes).  E.g. "jiminy cricket"@disney.com
       is a legal e-mail address. */

    var quotedUser="(\"[^\"]*\")";

    /* The following pattern applies for domains that are IP addresses,
       rather than symbolic names.  E.g. joe@[123.124.233.4] is a legal
       e-mail address. NOTE: The square brackets are required. */

    var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;

    /* The following string represents an atom (basically a series of non-special characters.) */

    var atom=validChars + '+';

    /* The following string represents one word in the typical username.
       For example, in john.doe@somewhere.com, john and doe are words.
       Basically, a word is either an atom or quoted string. */

    var word="(" + atom + "|" + quotedUser + ")";

    // The following pattern describes the structure of the user

    var userPat=new RegExp("^" + word + "(\\." + word + ")*$");

    /* The following pattern describes the structure of a normal symbolic
       domain, as opposed to ipDomainPat, shown above. */

    var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");

    /* Finally, let's start trying to figure out if the supplied address is valid. */

    /* Begin with the coarse pattern to simply break up user@domain into
       different pieces that are easy to analyze. */

    var matchArray=emailStr.match(emailPat);

    if (matchArray==null) {

        /* Too many/few @'s or something; basically, this address doesn't
           even fit the general mould of a valid e-mail address. */

        //alert("Email address seems incorrect (check @ and .'s)");
        alert("L'indirizzo email sembra non essere corretto (controlla chiocciole e punti)");
        return false;
    }
    var user=matchArray[1];
    var domain=matchArray[2];

    // Start by checking that only basic ASCII characters are in the strings (0-127).

    for (i=0; i<user.length; i++) {
        if (user.charCodeAt(i)>127) {
            //alert("Ths username contains invalid characters.");
            alert("Lo username della mail contiene caratteri non corretti.");
            return false;
        }
    }
    for (i=0; i<domain.length; i++) {
        if (domain.charCodeAt(i)>127) {
            //alert("Ths domain name contains invalid characters.");
            alert("Il dominio contiene caratteri non corretti.");
            return false;
        }
    }

    // See if "user" is valid 

    if (user.match(userPat)==null) {
        // user is not valid
        //alert("The username doesn't seem to be valid.");
        alert("Lo username della mail sembra non essere corretto");
        return false;
    }

    /* if the e-mail address is at an IP address (as opposed to a symbolic
       host name) make sure the IP address is valid. */

    var IPArray=domain.match(ipDomainPat);
    if (IPArray!=null) {
        // this is an IP address
        for (var i=1;i<=4;i++) {
            if (IPArray[i]>255) {
                //alert("Destination IP address is invalid!");
                alert("L'indirizzo IP di destinazione non e' corretto!");
                return false;
            }
        }
        return true;
    }

    // Domain is symbolic name.  Check if it's valid.
    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 domain name does not seem to be valid.");
            alert("Il dominio non sembra essere corretto.");
            return false;
        }
    }

    /* domain name seems valid, but now make sure that it ends in a
       known top-level domain (like com, edu, gov) or a two-letter word,
       representing country (uk, nl), and that there's a hostname preceding 
       the domain or country. */

    if (checkTLD && domArr[domArr.length-1].length!=2 && domArr[domArr.length-1].search(knownDomsPat)==-1) {
        //alert("The address must end in a well-known domain or two letter " + "country.");
        alert("L'indirizzo deve terminare con dominio conosciuto o con la country.");
        return false;
    }

    // Make sure there's a host name preceding the domain.

    if (len<2) {
        //alert("This address is missing a hostname!");
        alert("Indirizzo senza dominio!");
        return false;
    }

    // If we've gotten this far, everything's valid!
    return true;
}