Checking validity of email

[niyogi]

I saw in a book somewhere that there was some PHP trick that allows you to check the validity of an email address without actually having to send an email to the email address.

So essentially you would have a system that doesn't have any email bouncebacks. I could go to the bookstore and grab the code but maybe you guys know more about this. 😉

Thanks in advance!

-S

[risource]

Here's a simple "quick check". It simply pattern matches an email against
the pattern:

"any_number_of_valid_chars" followed by "@" followed by
"any_number_of_valid_chars" followed by "." followed by
"any_number_of_valid_chars"

From Wrox PHP book (not sure if Beginning PHP4 or Prof programming in PHP). Author's claim the simple check is enough for many uses.... I agree.

function EmailVerify($email) {
if ($email=="")return;
else
// put email verify code here. If valid, leave as is. If INVALID, set to null string

if (ereg("^{.+@.+\..+$",$email)){}
echo("email is valid");
}else{
echo("email is INvalid");
}
return $email
}

[Anon]

You can file a plethora of working and almost working email validation code if you look in the user notes in the php manual.

lookup email() and getmxrr()

[Anon]

Hi,
You can also check out this Regex Tutorial from PHPBuilder

http://www.phpbuilder.com/columns/dario19990616.php3?page=3

Quoted from the above tutorial, you can use

eregi (^{[a-z0-9-]+(.[a-z0-9-]+)@[a-z0-9-]+(.[a-z0-9-]+)$,} $email)

If it looks very confusing to you, just check out the URL above.

Hope this helps

Laura Brandt

Aletia Hosting - Full-Featured, Superfast Web Hosting
$9.95/mo: 200MB + 10GB, Cpanel, PHP4/MySQL, Multi-Domains
Email [e-mail] - AIM: AletiaSales - ICQ: 111160011

[niyogi]

Oops. Maybe I didn't make post a little clearer.

I've already validated the actual email format. What I really want to validate is whether there is actually a POP3 mailbox account that exists for the email address.

Here's in example:
Somebody enters [e-mail] on a mailing list. It's a valid email address but it's going to bounce because there's no mailbox called "billgates" on the phpbuilder.com mail server. So there's a script that verifies that the mailbox in fact exists.

Any help now? heh. 🙂

-S

[Anon]

You can't for the general case. The best you can do is verify that the mx record exists based upon getmxrr() (which isn't fullproof). If it was a local network you might be able to pull it off using shell command like finger.

Otherwise, you could fire off a message and check your mail spool for a MAILER-DAEMON but I haven't ever investigated doing so.

[risource]

Sounds like you are asking "can I process my database of 40 million email addresses and eliminate the inavalid ones, without actually sending any emails?"... that would be a very valuable utility indeed!

For the sake of content in this thread (for those who need it), I've included the below code which rather carefully inspects email addresses for format validity and more. It does NOT actually test if the emails are valid. Author notes at the top.

<?php
/*

---

This script from MySQL/PHP Database Applications
by Jay Greenspan and Brad Bulger

---

You are free to resuse the material in this
script in any manner you see fit. There is
no need to ask for permission or provide
credit.

---

*/

#CheckEmail
#
#mailbox = addr-spec ; simple address

/ phrase route-addr ; name & addr-spec

#
#route-addr = "<" [route] addr-spec ">"
#
#route = 1#("@" domain) ":" ; path-relative
#
#addr-spec = local-part "@" domain ; global address
#
#local-part = word *("." word) ; uninterpreted

; case-preserved

#
#domain = sub-domain ("." sub-domain)
#
#sub-domain = domain-ref / domain-literal
#
#domain-ref = atom ; symbolic reference
#
#atom = 1<any CHAR except specials, SPACE and CTLs>
#
#specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted-

/ "," / ";" / ":" / "\" / <"> ; string, to use

/ "." / "[" / "]" ; within a word.

#

; ( Octal, Decimal.)

#CHAR = <any ASCII character> ; ( 0-177, 0.-127.)
#ALPHA = <any ASCII alphabetic character>

; (101-132, 65.- 90.)

; (141-172, 97.-122.)

#DIGIT = <any ASCII decimal digit> ; ( 60- 71, 48.- 57.)
#CTL = <any ASCII control ; ( 0- 37, 0.- 31.)

character and DEL> ; ( 177, 127.)

#CR = <ASCII CR, carriage return> ; ( 15, 13.)
#LF = <ASCII LF, linefeed> ; ( 12, 10.)
#SPACE = <ASCII SP, space> ; ( 40, 32.)
#HTAB = <ASCII HT, horizontal-tab> ; ( 11, 9.)
#<"> = <ASCII quote mark> ; ( 42, 34.)
#CRLF = CR LF
#
#LWSP-char = SPACE / HTAB ; semantics = SPACE
#
#linear-white-space = 1*([CRLF] LWSP-char) ; semantics = SPACE

; CRLF => folding

#
#delimiters = specials / linear-white-space / comment
#
#text = <any CHAR, including bare ; => atoms, specials,

CR & bare LF, but NOT ; comments and

including CRLF> ; quoted-strings are

; NOT recognized.

#
#quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or

; quoted chars.

#
#qtext = <any CHAR excepting <">, ; => may be folded

"\" & CR, and including

linear-white-space>

#
#domain-literal = "[" *(dtext / quoted-pair) "]"
#
#
#
#
#dtext = <any CHAR excluding "[", ; => may be folded

"]", "\" & CR, & including

linear-white-space>

#
#comment = "(" *(ctext / quoted-pair / comment) ")"
#
#ctext = <any CHAR excluding "(", ; => may be folded

")", "\" & CR, & including

linear-white-space>

#
#quoted-pair = "\" CHAR ; may quote any char
#
#phrase = 1*word ; Sequence of words
#
#word = atom / quoted-string
#

#mailbox = addr-spec ; simple address

/ phrase route-addr ; name & addr-spec

#route-addr = "<" [route] addr-spec ">"
#route = 1#("@" domain) ":" ; path-relative
#addr-spec = local-part "@" domain ; global address

#validate_email("[e-mail]");

// boolean validate_email ([string email address])

// This function validates the format of an email address in a rather
// exhaustive manner, based on the relevant RFC. Note: this does
// NOT validate the email address in any functional way. Just because
// it looks OK doesn't mean it works.

function validate_email ($eaddr="")
{

if (empty($eaddr))
{

#print "[$eaddr] is not valid\n";
return false;
}
$laddr = "";
$laddr = $eaddr;

if the addr-spec is in a route-addr, strip away the phrase and <>s

$laddr = preg_replace('/^.*</','', $laddr);
$laddr = preg_replace('/>.*$/','',$laddr);
if (preg_match('/^\@.*:/',$laddr))	#path-relative domain
{
	list($domain,$addr_spec) = preg_split('/:/',$laddr);
	$domain = preg_replace('/^\@/','',$domain);
	if (!is_domain($domain)) { return false; }
	$laddr = $addr_spec;
}
return(is_addr_spec($laddr));

}

function is_addr_spec ( $eaddr = "" )
{
list($local_part,$domain) = preg_split('/@/',$eaddr);
if (!is_local_part($local_part) || !is_domain($domain))
{
#print "[$eaddr] is not valid\n";
return false;
}
else
{
#print "[$eaddr] is valid\n";
return true;
}
}

#local-part = word *("." word) ; uninterpreted
function is_local_part ( $local_part = "" )
{
if (empty($local_part)) { return false; }

$bit_array = preg_split('/\./',$local_part);
while (list(,$bit) = each($bit_array))
{
	if (!is_word($bit)) { return false; }
}
return true;

}

#word = atom / quoted-string
#quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or

; quoted chars.

#qtext = <any CHAR excepting <">, ; => may be folded

"\" & CR, and including

linear-white-space>

#quoted-pair = "\" CHAR ; may quote any char
function is_word ( $word = "")
{

if (preg_match('/^".*"$/i',$word))
{
	return(is_quoted_string($word));
}
return(is_atom($word));

}

function is_quoted_string ( $word = "")
{
$word = preg_replace('/^{"/','',$word);} # remove leading quote
$word = preg_replace('/"$/','',$word); # remove trailing quote
$word = preg_replace('/\+/','',$word); # remove any quoted-pairs
if (preg_match('/\"\\r/',$word)) # if ", \ or CR, it's bad qtext
{
return false;
}
return true;
}

#atom = 1*<any CHAR except specials, SPACE and CTLs>
#specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted-

/ "," / ";" / ":" / "\" / <"> ; string, to use

/ "." / "[" / "]" ; within a word.

#SPACE = <ASCII SP, space> ; ( 40, 32.)
#CTL = <any ASCII control ; ( 0- 37, 0.- 31.)

character and DEL> ; ( 177, 127.)

function is_atom ( $atom = "")
{

if (
(preg_match('/[\(\)\<\>\@\,\;\:\\\"\.\[\]]/',$atom))	# specials
	|| (preg_match('/\040/',$atom))			# SPACE
	|| (preg_match('/[\x00-\x1F]/',$atom))		# CTLs
)
{
	return false;
}
return true;

}

#domain = sub-domain *("." sub-domain)
#sub-domain = domain-ref / domain-literal
#domain-ref = atom ; symbolic reference
function is_domain ( $domain = "")
{

if (empty($domain)) { return false; }

this is not strictly required, but is 99% likely sign of a bad domain

if (!preg_match('/./',$domain)) { return false; }

$dbit_array = preg_split('/./',$domain);
while (list(,$dbit) = each($dbit_array))
{
	if (!is_sub_domain($dbit)) { return false; }
}
return true;

}
function is_sub_domain ( $subd = "")
{
if (preg_match('/^{[.]$/',$subd))} #domain-literal
{
return(is_domain_literal($subd));
}
return(is_atom($subd));
}
#domain-literal = "[" (dtext / quoted-pair) "]"
#dtext = <any CHAR excluding "[", ; => may be folded

"]", "\" & CR, & including

linear-white-space>

#quoted-pair = "\" CHAR ; may quote any char
function is_domain_literal ( $dom = "")
{
$dom = preg_replace('/\+/','',$dom); # remove quoted pairs
if (preg_match('/[[]\\r]/',$dom)) # bad dtext characters
{
return false;
}
return true;
}

// void print_validate_email ([string email address])

// This function prints out the result of calling the validate_email()
// function on a given email address.

function print_validate_email ($eaddr="")
{
$result = validate_email($eaddr) ? "is valid" : "is not valid";
print "<h4>email address (".htmlspecialchars($eaddr).") $result</h4>\n";
}

?>