Failed to get initial SMTP response..

Question:
I have 21 text message service applications running on a single PC. These apps send out weather alerts to radio station listeners several times a day. Each may have a few subscribers to a few hundred subscribers, so at the top of the hour, the messages for the people signed up for that hour are sent.
I sometimes get this error:

ErrorChilkatLog:
  SendEmail:
    DllDate: Aug 24 2008
    Username: User
    Component: ActiveX
    Recipients:
      NumTo: 1
      To: ****
      NumCC: 0
      NumBCC: 0
    Need new SMTP connection
    SMTP_Connect:
      Connecting to SMTP server mail.****.net:25
      smtp_host: mail.****.net
      smtp_port: 25
      smtp_user: abc@****.net
      numBytesRequested: 1000
      Connection closed by server.
      Socket is no longer readable
      InitialResponse:
      Failed to get initial SMTP response..
      The SMTP server may be denying access for this domain.
    Failed to connect to SMTP server.

Answer:

It’s possible that at times you have too many simultaneous connections to the SMTP server.  It may be that the SMTP server is immediately disconnecting from your program because of this condition.  Check your SMTP server configuration/settings to see if you can find anything related to the maximum number of sessions allowed.  It might also be caused by the fact that all sessions are coming from the same IP address, and the SMTP server might put a limit on this specific condition.

One possible solution is to have each instance of your application check and send email at different times.

Note: You may ignore this part of the error message:  “The SMTP server may be denying access for this domain.”  It only provides a suggestion for one possible cause of the problem.  If the SMTP server were denying access for the domain, you would either (1) never be able to establish the connection in the 1st place, or (2) every attempt to send email would fail.