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vinay pannalavinay pannala 

System.CalloutException: Unable to tunnel through proxy. Proxy returns "HTTP/1.1 503 Service Unavailable"

Hi Having this issue I am currently on VDSI and unable to make a callout dont know where the issue is was able to make a call from post man but from salesforce getting this error message.

System.CalloutException: Unable to tunnel through proxy. Proxy returns "HTTP/1.1 503 Service Unavailable"
Best Answer chosen by vinay pannala
Khan AnasKhan Anas (Salesforce Developers) 
Hi Vinay,

Greetings to you!

This error happens if your firewall doesn’t allow access to your server where the web service is hosted. Making the firewall changes should fix this issue.

In general, when you see an issue, follow this checklist to troubleshoot the issue:
  • Make sure you have the firewall settings in your enterprise is configured to allow the inbound web service call.
  • Check whether the certificate is expired or not.
  • Check if your chain of trust has valid certificates.

Also, check whether you have white-listed salesforce IP's in their proxy: http://www.salesforcegeneral.com/salesforce-articles/ip-whitelists-for-salesforce.html

I hope it helps you.

Kindly let me know if it helps you and close your query by marking it as solved so that it can help others in the future. It will help to keep this community clean.

Thanks and Regards,
Khan Anas

All Answers

Khan AnasKhan Anas (Salesforce Developers) 
Hi Vinay,

Greetings to you!

This error happens if your firewall doesn’t allow access to your server where the web service is hosted. Making the firewall changes should fix this issue.

In general, when you see an issue, follow this checklist to troubleshoot the issue:
  • Make sure you have the firewall settings in your enterprise is configured to allow the inbound web service call.
  • Check whether the certificate is expired or not.
  • Check if your chain of trust has valid certificates.

Also, check whether you have white-listed salesforce IP's in their proxy: http://www.salesforcegeneral.com/salesforce-articles/ip-whitelists-for-salesforce.html

I hope it helps you.

Kindly let me know if it helps you and close your query by marking it as solved so that it can help others in the future. It will help to keep this community clean.

Thanks and Regards,
Khan Anas
This was selected as the best answer
Moin AhamadMoin Ahamad
Hi Khan Anas,
I tried doing above things which was mentioned by you but at my server end I'm able to allow the request from country name not base on IP Range. Can you please help me how can I fix this issue.
Thanks