When Outlook is unable to connect to the proxy server, error code 18 typically indicates that the server's address is incorrect. This can happen if the proxy server was recently changed and Outlook has not been updated with the new information. It can also occur if there is a typographical error in the server's address.
If you are using a corporate proxy server, you may need to contact your network administrator for assistance. In some cases, you may need to configure your browser to use the proxy server. Once the proxy server is correctly configured, Outlook should be able to connect without issue.
1. Try to connect to the proxy server again
- Open Outlook and click on the File tab.
- Select Options from the menu.
- Click on the Advanced tab.
- Under the Connections heading, click on the Proxies tab.
- Locate the proxy server that Outlook is using and click on the Connect button.
- Enter the proxy server's address and port number into the appropriate fields and click on the OK button.
- Click on the OK button again to close the Options window.
- Click on the OK button once more to close Outlook.
2. Check your proxy server settings and make sure they are correct
- Open the "Internet Options" window by clicking on the "Start" button, typing "Internet Options" in the search box, and hitting "enter."
- Click on the "Connections" tab, and then click on the "Proxies" tab.
- In the "Proxies" tab, click on the "Use a proxy server" button.
- In the "Proxy server address" box, type the proxy server address that you use to connect to the internet.
- In the "Proxy port" box, type the proxy port that you use to connect to the internet.
- In the "Use a proxy server for local addresses" box, check the box to use the proxy server for local addresses.
- Click on the "OK" button.
- Close the "Internet Options" window.
- Try to connect to the Outlook server using the proxy server address and proxy port that you set in step 7.
3. Restart your computer and try to connect to the proxy server again
Open your browser and type the following into the address bar: http://proxyserveraddress:port/ For example, if your proxy server is located at http://192.168.1.100:8080, you would enter http://proxyserveraddress:port/ in your browser. If you are using a proxy server that is not hosted by your employer, you will need to provide the proxy server address and port.
If the answers above didn't work then you should also try:
- Check your internet connection and make sure it is working properly.
- Contact your network administrator and ask them for help.