verify if a given email address is exist

Hi,
I wrote an application with VS2005 to send mail to a subscriber base,
while the application works fine. I am trying to find a way to reduce
email address bounce backs, is there a .Net (or command line) method
via which I could verify if a given email address is exist.

To clarify, I am trying to validate beyond the domain, I would like to
validate if the mailbox is present at a SMTP server, so that I can
ping the gmail SMTP server to see if mailbox123@gmail.com does not
exist in their server so that my application will not sent the email.

Any pointers would be greatly appreciated..

btw, I looked into Telnet's VRFY but apparently is not supported under
windows???

Thanks in advanced,
Raf

Re: verify if a given email address is exist

First and foremost, this is not a (Unix) Sendmail (Mail Transfer Agent)
related question, thus is not directly applicable to this news group.

On 11/5/2007 8:47 PM, RGF wrote:
> I wrote an application with VS2005 to send mail to a subscriber base,
> while the application works fine. I am trying to find a way to
> reduce email address bounce backs, is there a .Net (or command line)
> method via which I could verify if a given email address is exist.
>
> To clarify, I am trying to validate beyond the domain, I would like
> to validate if the mailbox is present at a SMTP server, so that I can
> ping the gmail SMTP server to see if mailbox123@gmail.com does not
> exist in their server so that my application will not sent the email.
>
> Any pointers would be greatly appreciated..

There are a few things you can do:
- Try the VRFY command to see if an address is rejected.
- Try to deliver the message and see if the address is rejected.
- Use VERP to (more) intelligently handle bounces.
- Use DSN "notify" and "ret" parameters to control how much and when
you receive bounces.

Variable Envelope Return Path (a.k.a. VERP) is a technique where you
send to each recipient with a different source address. This way you
can be assured that any bounces that come in are related to the specific
associated original destination address.

Delivery Status Notification (a.k.a. DSN) is a technique to ask
supporting mail servers to notify you about success and / or failures of
deliveries of messages. You can also ask that either the headers of the
original message or the entire original message be sent back to you in
the DSN. Headers are nicer than the entire message as they do not take
up nearly as much space.

> btw, I looked into Telnet's VRFY but apparently is not supported
> under windows???

This is an MTA specific issue. Seeing as how you are referencing
Windows, I'm going to presume that you are referring to IIS in
conjunction with Exchange. I don't know if this is or is not the case,
with IIS / Exchange, however this is likely to be a version /
configuration issue.

> Thanks in advanced,

*nod*



Grant. . . .

Re: verify if a given email address is exist

On Nov 5, 10:09 pm, Grant Taylor wrote:

> First and foremost, this is not a (Unix) Sendmail (Mail Transfer Agent)
> related question, thus is not directly applicable to this news group.
>
> On 11/5/2007 8:47 PM, RGF wrote:
>
> > I wrote an application with VS2005 to send mail to a subscriber base,
> > while the application works fine. I am trying to find a way to
> > reduce email address bounce backs, is there a .Net (or command line)
> > method via which I could verify if a given email address is exist.
>
> > To clarify, I am trying to validate beyond the domain, I would like
> > to validate if the mailbox is present at a SMTP server, so that I can
> > ping the gmail SMTP server to see if mailbox...@gmail.com does not
> > exist in their server so that my application will not sent the email.
>
> > Any pointers would be greatly appreciated..
>
> There are a few things you can do:
> - Try the VRFY command to see if an address is rejected.
> - Try to deliver the message and see if the address is rejected.
> - Use VERP to (more) intelligently handle bounces.
> - Use DSN "notify" and "ret" parameters to control how much and when
> you receive bounces.
>
> Variable Envelope Return Path (a.k.a. VERP) is a technique where you
> send to each recipient with a different source address. This way you
> can be assured that any bounces that come in are related to the specific
> associated original destination address.
>
> Delivery Status Notification (a.k.a. DSN) is a technique to ask
> supporting mail servers to notify you about success and / or failures of
> deliveries of messages. You can also ask that either the headers of the
> original message or the entire original message be sent back to you in
> the DSN. Headers are nicer than the entire message as they do not take
> up nearly as much space.
>
> > btw, I looked into Telnet's VRFY but apparently is not supported
> > under windows???
>
> This is an MTA specific issue. Seeing as how you are referencing
> Windows, I'm going to presume that you are referring to IIS in
> conjunction with Exchange. I don't know if this is or is not the case,
> with IIS / Exchange, however this is likely to be a version /
> configuration issue.
>
> > Thanks in advanced,
>
> *nod*
>
> Grant. . . .

>From looking at the forum header I was clear if it meant to cover
sendmail (as in sending mail) issues in general...

Thanks for the above pointers, which are definitely beyond my scope of
knowledge, hence the initial post. I will be googling some of the
concepts you mentioned above.

To be more specific, I am using Win XP SP2 with PostCast (a relatively
light SMTP server, and from time to time I use minirelay from the
command line)

I also discovered after posting that VRFY (or the lack of support) is
not present in MTA, I downloaded PuTTy in order t access a robust
Telnet client... but my initial tries at VRFY have been futile, but I
am certain is my syntax.. I will repost this thread on a more
appropriate forum..

Raf

Re: verify if a given email address is exist

On 11/06/07 08:02, RGF wrote:
> From looking at the forum header I was clear if it meant to cover
> sendmail (as in sending mail) issues in general...

Sendmail in this case is the name of a program, not the act of sending
email. As such, you are accidentally in the wrong location to be asking
these questions.

I'm willing to try to help you solve your issue(s), however they should
be done out side of this news group.

> Thanks for the above pointers, which are definitely beyond my scope
> of knowledge, hence the initial post. I will be googling some of the
> concepts you mentioned above.

*nod* Drop me a direct email if you would like to discuss things.

> To be more specific, I am using Win XP SP2 with PostCast (a
> relatively light SMTP server, and from time to time I use minirelay
> from the command line)

I can't say as if I've heard of them, so I can not comment on them.

> I also discovered after posting that VRFY (or the lack of support) is
> not present in MTA, I downloaded PuTTy in order t access a robust
> Telnet client... but my initial tries at VRFY have been futile, but I
> am certain is my syntax.. I will repost this thread on a more
> appropriate forum..

The VRFY ESMTP verb is often either not implemented or has been disabled
for security / anti-spam reasons. It is entirely possible that the SMTP
server you are trying to use them with does not support it and / or has
it disabled.

If you would like to continue discussing this, please reply to me directly.



Grant. . . .

Re: verify if a given email address is exist

On Tue, 06 Nov 2007, in the Usenet newsgroup comp.mail.sendmail, in article
<1194357744.111815.69960@57g2000hsv.googlegroups.com>, RGF wrote:

>Grant Taylor wrote:

>> First and foremost, this is not a (Unix) Sendmail (Mail Transfer Agent)
>> related question, thus is not directly applicable to this news group.

>> RGF wrote:

>>> I wrote an application with VS2005 to send mail to a subscriber base,
>>> while the application works fine. I am trying to find a way to
>>> reduce email address bounce backs, is there a .Net (or command line)
>>> method via which I could verify if a given email address is exist.

Did you fail to get a confirmation from each subscriber when the mailing
list was created? That's terribly risky.

You might consider sending a short request for confirmation to each
address, and remove those addresses that bounce (obviously bad) or that
do not return the confirmation within a day or two (not interested).

>From looking at the forum header I was clear if it meant to cover
>sendmail (as in sending mail) issues in general...

It's not a google web forum, but a Usenet newsgroup. On the 15th of
each month, there is a posting to the newsgroups news.announce.newgroups,
news.groups, and news.lists.misc with the subject "List of Big Eight
Newsgroups". For this group, it lists

[compton ~]$ grep sendmail big.8.list.10.15.07
comp.mail.sendmail Configuring and using the BSD sendmail agent.
[compton ~]$

What _might_ be more useful is

[compton ~]$ grep list-admin big.8.list.10.15.07
comp.mail.list-admin.policy Policy issues in running mailing lists.
comp.mail.list-admin.software Software used in the running of mailing lists.
[compton ~]$

>I also discovered after posting that VRFY (or the lack of support) is
>not present in MTA, I downloaded PuTTy in order t access a robust
>Telnet client... but my initial tries at VRFY have been futile, but I
>am certain is my syntax.. I will repost this thread on a more
>appropriate forum..

0821 Simple Mail Transfer Protocol. J. Postel. August 1982. (Format:
TXT=124482 bytes) (Obsoletes RFC0788) (Obsoleted by RFC2821) (Also
STD0010) (Status: STANDARD)

2821 Simple Mail Transfer Protocol. J. Klensin, Ed.. April 2001.
(Format: TXT=192504 bytes) (Obsoletes RFC0821, RFC0974, RFC1869,
STD0010) (Status: PROPOSED STANDARD)

See RFC821 and/or 2821. Be aware that because of abuse, some systems
may not accept VRFY commands.

Old guy