SMTP server intermittent problem

[Guest WAFDOF]

I have an unusual issue that I believe it related to a setting in the IIS

SMTP Virtual Server Settings.

 

I have an intermittent problem where an email sent by a small asp.net

application would fail to send the exception was "Error receiving data from

socket." The VB error message generated related to "The transport failed to

connect to the server. "

 

I spent a bit of time troubleshooting the asp code only to have the same

results...sometimes the emails would process and sometimes they would

not.....no variable changed at all.

 

In an attemtp to find a pattern to the problem and rule out asp.net code I

wrote a very small windows application that sends an email once a minute and

reports back the results. I was amazed to find a solid pattern and this is

where I could use some help pointing me in the right direction.

 

The sever sends an email once a minute and the first 9 emails send fine but

the next 9 emails will fail to send and then the pattern repeats itself the

next 9 emails go fine, then will send 9 emails that fail...etc.

 

Nothing changed in the settings...each email was sent using hardcoded

variables so there would be no difference in the TO: FROM: SUBJECT: SMTP

SERVER: or BODY.

 

I have run this for several hours always with the same pattern revealing

itself, 9 times it will send email then 9 times it will fail then 9 times it

will send and so on.

 

Now for the server details. This is a development server running behind out

INTRANET firewall. All virus software has been disabled. The Firewall on

the server has been disabled. The application is running ON the server. The

situation manifiest itself both in using windows applications and Web pages

(asp.net).

 

These are the current property settings of the virtual server:

 

IP Address is within the IP range of the intranet - 10.16.56.9

Connections limited to 100

connection time-out in minutes 5

Under advanced theIP Address and TCP Port are 10.15.56.9 25

 

Access tab - Anonymous access is checked

connection control as access granted to 10.16.56.9

relay restictions are granted to 10.16.56.9

connection control grrants access for 10.16.56.9 to the virtual server

 

Messages tab

Message size limited to 2048 KB

Session size limited to 10240KB

Limit number of message per connection to 100

Limit number of recipients to 100

 

Delivery tab

First realy interval minutes 15

Second retry 30

third retry 60

subsequent retry 240

delay notification 12 min

Expiration timeout 30 min

Loca delay 24 min

Expiration timeout 12 min

 

Outbound security set to anonymous access

Outbound connections limited to 1000

time-out 2 minutes

number of connections per domaim 100

TCP port 25

 

These settings have been changed a few times as I gleen what I can from the

internet. I have stopped and started the the SMTP Virtual Server on variable

changes without effect.

 

The TO: from: variables for the email are valid as they have been checked

and email is actually sent and received using the same variables.

 

Obviously I am curious about the pattern I have discovered. Each minute an

identical email is sent...and as I have said the first 9 times the email goes

fine then the next 9 times it will fail and then the next 9 times it will go

fine..and so on. I have not been able to find a variable in the SMTP

porperties that is tied to this apparent 10 min cycle.

 

This server does not touch the INTERNET and the SMTP mail being sent stays

within the intranet of our organization.

 

What additional information may be needed to look into the unusual

circumstance?

 

WAFDOF