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Windows Server Port Conflicts

LDAP Server Conflict

When you run VPOP3 on a server edition of Windows you may receive an error saying

LDAP server not started - couldn't bind socket port 389 (10048)

This error happens because VPOP3 contains an LDAP (Lightweight Directory Access Protocol) server for its global address book functionality, and the Windows 2000/2003 'Active Directory Service' also uses LDAP as its mechanism. These two services are conflicting.

The solution is to either remove the VPOP3 LDAP service or move it to a different port number.

  • To remove the VPOP3 LDAP service, go to the Services page in the VPOP3 settings, and remove the tick in the Enable checkbox on the LDAP Server line. NB - This will stop the VPOP3 Global Address book from working.
  • To move the VPOP3 LDAP service to a different port, go to the Services page in the VPOP3 settings, and in the Port column on the LDAP Server line, change the number to something like 1389 (it should be greater than 1000 and mustn't conflict with any other TCP/IP service, we generally find that adding 1000 to the standard port number is the easiest to remember).

After any of these changes you will have to restart the VPOP3 software.

If you move the VPOP3 LDAP service, you will have to tell all your email clients that are using the VPOP3 Global Address Book to use the new port number. This is done in the email client settings, and depends on the particular email client you are using. In general look for something called Directory Service or LDAP Service.

SMTP Server conflict

You may also get a similar 10048 error referring to the VPOP3 SMTP server, or you may get unusual errors when sending messages to the VPOP3 SMTP service. In this case, it may be due to the Microsoft 'Simple Mail Transfer Protocol' service running.

Usually the best thing to do in this situation is to disable to Microsoft service - go to Control Panel → Administrative Tools → Services, and stop and disable the Simple Mail Transfer Protocol service (or the Microsoft Simple Mail Transfer Protocol service), then restart VPOP3.

faq/windows_server_port_conflicts.txt · Last modified: 2018/11/14 10:45 (external edit)