Hi to all.
I want check the address not the sintax.
Regards.

César,

>I want check the address not the sintax.

The answer to your question is: No.

The only way to verify that an Email address is valid is to send an email 
and wait for a response. If you don't get an error response from the email 
server, you can assume that the email address is valid. But, you can't prove 
a negative, so the absence of an error response doesn't guarantee that the 
email address is valid, just that the email server didn't send a negative 
response. 

For example, if you use -- for whatever reason -- an invalid "From:" header, 
you won't receive a response. Also, some email servers are configured to 
not respond to invalid email addresses, to prevent someone from determining 
which email addresses are valid. As email addresses are more and more used 
as login names into all kinds of systems, just knowing that an email address 
is valid, is sometimes considered a security risk.

Hope that helps,

Andreas

Andreas Gehrs-Pahl
Absolute Software, LLC

phone: (989) 723-9927
email: Andreas.GP@Charter.net
web:   http://www.Aerospace-History.net

The answer is: yes. But it's not very easy.

Example: Just look how email works and use the telnet command.

 >telnet mailserver.domain.tld 25
Wait for the 220 Message.
 >helo mail
Wait for the 250 Message.
This is to start the conversation with the mail server.
 >mail from: <valid.mailaddress@domain.tld>
Some mail server will do also an test.
Wait for the 250 Message.
 >rcpt to: <valid.mailaddress_to_test@domain.tld>
This is you Mailaddress.
Wait for the 250 Message. --> The Mailaddress exists.
If you get here an 251 Message, then the server usese graylisting, and 
it is not possible to check the mail at this time. Look at the message 
to see how long you have to wait. There are many technikes to avoid 
spam, you must handle. Hard work at thit point. Try yourself with 
different mailservers and look what they will answer.
 >quit
Wait for the 221 Message.
Use 'exit' to close the telnet command.

Ulrich

On 29.05.14 06:45, César Calvo wrote:
> Hi to all.
> I want check the address not the sintax.
> Regards.

Gerd,

>The answer is: yes. But it's not very easy.

Exactly. This is way more complicated than sending an email as a test. For 
example, the first step is to determine the mail server name for the domain 
you are sending the email to, which isn't as straight forward as adding a 
sub domain of "smtp" or "mail" to the email address domain. So you need to 
look up MX records first.

The second problem are SSL/TLS-only email servers, so on GMail for example, 
you will get the following response to the "mail from: ..." command:

530 5.7.0 Must issue a STARTTLS command first. ... - gsmtp

Another problem is that many -- especially corporate mail servers -- don't 
give that information to just any telnet connection. Many use reputation-
based white listing, and more than often, you will get something like this 
after the: "rcpt to: ..." message:

550 Invalid HELO/EHLO
or
554 Service unavailable; Client host [...] blocked using [...]

Anyway, you might be able to do this on a case by case basis, but not using 
a simple algorithm, based only on the recipient's email address.

Andreas

Andreas Gehrs-Pahl
Absolute Software, LLC

phone: (989) 723-9927
email: Andreas.GP@Charter.net
web:   http://www.Aerospace-History.net