1. Antivirus software block connection from Outlook to the Exchange server.
2. Firewall block connection from Outlook to the Exchange server.
3. Outlook 2003 has been installed on Exchange 2003 Server/domain controller.
4. Outlook profile has been Corrupted.
5. Exchange database has been corrupted (usually this occur if some third party software - like antivirus - scan Exchange database directly).
2. Verity that you use antivirus software that compatible to Exchange 2003 and Outlook 2003.
3. If the outlook and Exchange server insulated from each other by using firewall, there may need to configure static port mapping:
4. Check Exchange database by using Eseutil Utility and Isinteg Utility.
5. Delete old outlook profile and create a new profile.
6. If Outlook 2003 has been installed on Exchange server/domain controller, there need to change the security settings of "log on network security" to "Kerberos
Password Authentication" ("Kerberos/NTLM Password Authentication" - the default settings - may fail to use correct authentication model).
XADM: Description of the Isinteg Utility
Using Exchange Server 2003 Recovery Storage Groups
Exchange 2000 and Exchange 2003 Static Port Mappings
Article ID: 555049 - Last Review: 14 Feb 2017 - Revision: 1