Microsoft CDONTS/Microsoft SMTP Service fails to send mail


Microsoft CDONTS/CDOSYS fails to send mails generated with the CDOSYS object. Some customized web forms or applications may use CDONTS to dispatch messages. 


CDONTS requires the Microsoft SMTP service in order to send out email. But it is not possible to have two mail servers running on port 25 and the same IP address trying to receive email at the same time.

There are two solutions to this problem.

Solution One

Run the Microsoft SMTP service inbound port on something other than the MailEnable port (i.e. not port 25). Leave the outbound port as port 25, since both Microsoft SMTP and MailEnable SMTP can send email at the same time. The steps for changing the inbound port for the Microsoft SMTP service are listed below:

  1. Open Internet Information Services (accessed in Windows 2000 through the Administrative Tools Control Panel folder)
  2. Expand the tree view to locate "Default SMTP Virtual Server"
  3. Right click on this icon and select Properties from the pop up menu.
  4. In the General tab, select "Advanced" next to the IP address that the SMTP service is bound to. A new window will open up.
  5. Select the IP address. Usually this is called (All Unassigned), but may be a particular IP address. This opens a new window.
  6. Change the TCP Port to something other than 25.
  7. Accept the changes
  8. Stop and start both the Microsoft and MailEnable SMTP services.

Solution Two

Use components other than CDONTS. A component is included in the MailEnable Professional and Enterprise Editions that allows email to be sent from ASP.


How to send mail from ASP pages with MailEnable:

Product:MailEnable (All Versions)
Class:PRB: Problem (Configuration or Environment)
Created:31/01/2002 2:27:00 PM
Revised:Wednesday, May 4, 2016