SmtpMail connection question.

[Guest]

I've got 2 different applications that use the same SMTP server. One is
written in C# and uses the SmtpMail class. The other is in C++ and uses the
ATL CSMTPConnction class. The SmtpMail code works just fine. The
CSMTPConnection code fails. In digging down into the ATL code, I can see
where it issues a "HELO" command to the smtp server and reads the result to
check for a "250" return code as an indicator of success. Using telnet, I
can verify that 250 is returned from a "HELO" command. The big wrinkle here
is that the smtp server is using a 3rd party smtp security product. I
suspect that the ATL code is doing something that the 3rd party product does
not like. So, finally, my question is about how the SmtpMail class is
successful. Does the underlying code issue a "HELO" command at all?

TIA - Mitch

 

[Kevin Spencer]

Can you monitor both sides of the conversation? That is, using Ethereal
(free from Ethereal.com), or some other packet sniffer, check the entire
conversation, both client and server.

--
HTH,

Kevin Spencer
Microsoft MVP
Professional Numbskull

Hard work is a medication for which
there is no placebo.

 

[Ben Voigt]

Every SMTP connection needs to start with either HELO or EHLO (extended
HeLOo).

But then it's going to possibly start SSL (in which case Ethereal won't help
much) and then go on with "MAIL FROM: sender" and "RCPT TO: recipient"
(possibly multiple times) then "DATA" followed by the MIME wrapped message
and then a period "." on a line by itself which will go back to command
mode.

http://cr.yp.to/smtp/mail.html

 

[Guest]

Unfortunately, I do not have access to the SMTP server, so I am having to
deduce all of this from logging information. I do know that the the failing
code is returning
FALSE from AtlSmtpSendAndCheck(...) which could be returning false from
calls to either AtlSmtpSendAndWait(...) which uses WriteFile() to write "HELO
[hostname]" to the socket handle or AtlSmtpReadData(...) which uses
ReadFile() to get the response and check for the "250" code in the first 3
characters. Since I don't have access to the SMTP server, I was hoping to
deduce what the problem could be based on the fact that the SmtpMail class
had no problem at all using the same server.

FYI - When using telnet to check the response to "HELO", the response is the
following ( "xxxxx" for the brand of the proxy & replaced hostnames as well ).

220-xxxxxx SMTP proxy
220 a.b.c ESMTP server ready at Thu, 4 May 2006 09:47:35 +0200
helo myclient
250 a.b.c Hello localhost [127.0.0.1], pleased to meet you

The "Hello localhost [127.0.0.1]" jumped out at me since I expected the IP
address of the calling client. However, that doesn't explain why the SMTPMail
class works.

Sorry I can't provide any better info. Your comments are much appreciated!

 

[Cowboy \(Gregory A. Beamer\)]

It is possible the SMTP is setup to use Extended HELO instead of the basic
implementation. This is actually fairly common. By switching to EHLO, your
mail will start again. This should not be a major undertaking, but it could
add a bit of work to your plate.

--
Gregory A. Beamer

*************************************************
Think Outside the Box!
*************************************************

 

[Kevin Spencer]

Unfortunately, I do not have access to the SMTP server, so I am having to

deduce all of this from logging information. I do know that the the
failing
code is returning

Remember that a network connection is like a phone call. You don't have to
be on both ends to hear both sides of the conversation. If you put a packet
sniffer on the client, it will hear both sides on the client end. I have
found Ethereal to be priceless (literally, in fact!) for debugging networked
applications.

--
HTH,

Kevin Spencer
Microsoft MVP
Professional Numbskull

Hard work is a medication for which
there is no placebo.

Unfortunately, I do not have access to the SMTP server, so I am having to
deduce all of this from logging information. I do know that the the
failing
code is returning
FALSE from AtlSmtpSendAndCheck(...) which could be returning false from
calls to either AtlSmtpSendAndWait(...) which uses WriteFile() to write
"HELO
[hostname]" to the socket handle or AtlSmtpReadData(...) which uses
ReadFile() to get the response and check for the "250" code in the first 3
characters. Since I don't have access to the SMTP server, I was hoping to
deduce what the problem could be based on the fact that the SmtpMail class
had no problem at all using the same server.

FYI - When using telnet to check the response to "HELO", the response is
the
following ( "xxxxx" for the brand of the proxy & replaced hostnames as
well ).

220-xxxxxx SMTP proxy
220 a.b.c ESMTP server ready at Thu, 4 May 2006 09:47:35 +0200
helo myclient
250 a.b.c Hello localhost [127.0.0.1], pleased to meet you

The "Hello localhost [127.0.0.1]" jumped out at me since I expected the IP
address of the calling client. However, that doesn't explain why the
SMTPMail
class works.

Sorry I can't provide any better info. Your comments are much
appreciated!

Every SMTP connection needs to start with either HELO or EHLO (extended
HeLOo).

But then it's going to possibly start SSL (in which case Ethereal won't
help
much) and then go on with "MAIL FROM: sender" and "RCPT TO: recipient"
(possibly multiple times) then "DATA" followed by the MIME wrapped
message
and then a period "." on a line by itself which will go back to command
mode.

http://cr.yp.to/smtp/mail.html