function ValidateEmail (emailStr) {
/* Pattern to check if the entered e-mail address fits the user@domain format. */
var emailPat=/^(.+)@(.+)$/

/* Pattern to check for special characters we don't want, including ( ) < > @ , ; : \ " . [ ] */
var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]"

/* The following string represents the range of characters allowed in a username or domainname */
var validChars="\[^\\s" + specialChars + "\]"

/* The following pattern applies if the "user" is a quoted string, E.g. "jiminy cricket"@disney.com */
var quotedUser="(\"[^\"]*\")"

/* Pattern 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@themorgue.hell, john and doe are words */
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("E-mail adressen er indtastet forkert.(check @ og punktummer)")
 msgflag = "true";
return false
}
var user=matchArray[1]
var domain=matchArray[2]

// See if "user" is valid 
if (user.match(userPat)==null) {
// user is not valid
alert("Dit brugernavn er ugyldigt.")
 msgflag = "true";
return false
}

/* if the e-mail address is at an IP address 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("Destinationens IP adresse er ukorrekt!")
 msgflag = "true";
return false
}
}
return true
}

// Domain is symbolic name
var domainArray=domain.match(domainPat)
if (domainArray==null) {
alert("Domænenavnet er ugyldigt.")
 msgflag = "true";
return false
}

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

/* Now we need to break up the domain to get a count of how many atoms it consists of. */
var atomPat=new RegExp(atom,"g")
var domArr=domain.match(atomPat)
var len=domArr.length
if (domArr[domArr.length-1].length<2 || domArr[domArr.length-1].length>3) {
// the address must end in a two letter or three letter word.
alert("Adressen skal ende på et domæne med 3 bogstaver eller en landkode på 2 bogstaver .")
 msgflag = "true";
return false
}

// Make sure there's a host name preceding the domain.
if (len<2) {
var errStr="This address is missing a hostname!"
alert(errStr)
 msgflag = "true";
return false
}

// If we've gotten this far, everything's valid!

return true;
}