Email
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<?php
/************************************************************************
* This function checks the format of an email address. There are five levels of
* checking:
*
* 1 - Basic format checking. Ensures that:
* There is an @ sign with something on the left and something on the right
* To the right of the @ sign, there's at least one dot, with something to the left and right.
* To the right of the last dot is either 2 or 3 letters, or the special case "arpa"
* 2 - The above, plus the letters to the right of the last dot are:
* com, net, org, edu, mil, gov, int, arpa or one of the two-letter country codes
* 3 - The above, plus attempts to check if there is an MX (Mail eXchange) record for the
* domain name.
* 4 - The above, plus attempt to connect to the mail server
* 5 - The above, plus check to see if there is a response from the mail server. The third
* argument to this function is optional, and sets the number of times to loop while
* waiting for a response from the mail server. The default is 15000. The actual waiting
* time, of course, depends on such things as the speed of your server.
*
* Level 1 is bulletproof: if the address fails this level, it's bad. Level 2 is still
* pretty solid, but less certain: there could be valid TLDs overlooked when writing
* this function, or new ones could be added. Level 3 is even less certain: there are
* a number of things that could prevent finding an MX record for a valid address
* at any given time. 4 and 5 are even less certain still. Ultimately, the only absolutely
* positive way to test an email address is to send something to it.
*
* The function returns 0 for a valid address, or the level at which it failed, for an
* invalid address.
*
************************************************************************/
function MailVal($Addr, $Level, $Timeout = 15000) {
// Valid Top-Level Domains
$gTLDs = "com:net:org:edu:gov:mil:int:arpa:";
$CCs = "ad:ae:af:ag:ai:al:am:an:ao:aq:ar:as:at:au:aw:az:ba:bb:bd:be:bf:".
"bg:bh:bi:bj:bm:bn:bo:br:bs:bt:bv:bw:by:bz:ca:cc:cf:cd:cg:ch:ci:".
"ck:cl:cm:cn:co:cr:cs:cu:cv:cx:cy:cz:de:dj:dk:dm:do:dz:ec:ee:eg:".
"eh:er:es:et:fi:fj:fk:fm:fo:fr:fx:ga:gb:gd:ge:gf:gh:gi:gl:gm:gn:".
"gp:gq:gr:gs:gt:gu:gw:gy:hk:hm:hn:hr:ht:hu:id:ie:il:in:io:iq:ir:".
"is:it:jm:jo:jp:ke:kg:kh:ki:km:kn:kp:kr:kw:ky:kz:la:lb:lc:li:lk:".
"lr:ls:lt:lu:lv:ly:ma:mc:md:mg:mh:mk:ml:mm:mn:mo:mp:mq:mr:ms:mt:".
"mu:mv:mw:mx:my:mz:na:nc:ne:nf:ng:ni:nl:no:np:nr:nt:nu:nz:om:pa:".
"pe:pf:pg:ph:pk:pl:pm:pn:pr:pt:pw:py:qa:re:ro:ru:rw:sa:sb:sc:sd:".
"se:sg:sh:si:sj:sk:sl:sm:sn:so:sr:st:su:sv:sy:sz:tc:td:tf:tg:th:".
"tj:tk:tm:tn:to:tp:tr:tt:tv:tw:tz:ua:ug:uk:um:us:uy:uz:va:vc:ve:".
"vg:vi:vn:vu:wf:ws:ye:yt:yu:za:zm:zr:zw:";
// The countries can have their own 'TLDs', e.g. mydomain.com.au
$cTLDs = "com:net:org:edu:gov:mil:co:ne:or:ed:go:mi:";
$fail = 0;
// Shift the address to lowercase to simplify checking
$Addr = strtolower($Addr);
// Split the Address into user and domain parts
$UD = explode("@", $Addr);
if (sizeof($UD) != 2 || !$UD[0]) $fail = 1;
// Split the domain part into its Levels
$Levels = explode(".", $UD[1]); $sLevels = sizeof($Levels);
if ($sLevels < 2) $fail = 1;
// Get the TLD, strip off trailing ] } ) > and check the length
$tld = $Levels[$sLevels-1];
$tld = ereg_replace("[>)}]$|]$", "", $tld);
if (strlen($tld) < 2 || strlen($tld) > 3 && $tld != "arpa") $fail = 1;
$Level--;
// If the string after the last dot isn't in the generic TLDs or country codes, it's invalid.
if ($Level && !$fail) {
$Level--;
if (!ereg($tld.":", $gTLDs) && !ereg($tld.":", $CCs)) $fail = 2;
}
// If it's a country code, check for a country TLD; add on the domain name.
if ($Level && !$fail) {
$cd = $sLevels - 2; $domain = $Levels[$cd].".".$tld;
if (ereg($Levels[$cd].":", $cTLDs)) { $cd--; $domain = $Levels[$cd].".".$domain; }
}
// See if there's an MX record for the domain
if ($Level && !$fail) {
$Level--;
if (!getmxrr($domain, $mxhosts, $weight)) $fail = 3;
}
// Attempt to connect to port 25 on an MX host
if ($Level && !$fail) {
$Level--;
while (!$sh && list($nul, $mxhost) = each($mxhosts))
$sh = fsockopen($mxhost, 25);
if (!$sh) $fail = 4;
}
// See if anyone answers
if ($Level && !$fail) {
$Level--;
set_socket_blocking($sh, false);
$out = ""; $t = 0;
while ($t++ < $Timeout && !$out)
$out = fgets($sh, 256);
if (!ereg("^220", $out)) $fail = 5;
}
if ($sh) fclose($sh);
return $fail;
} //MailVal
?>
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Usage Example
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<?
if (MailVal($Address, 2)) echo "Invalid address";
?>
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