I am just starting to explore Postman (win10, behind lots of corporate firewalls and proxies).

I had no problem reaching https://postman-echo.com for GET and POST requests.

But we have an internal website that has a self-sign certificate which also pops up a username/password request in Chrome (It seems it using Basic Auth) Anyway the GET request works when put the URL box. https://epicorapp2/ERP10.1Test/api/v1/Erp.BO.JobEntrySvc/JobEntries?%2524top=1

Here is what I have done:

  1. Used settings to turn off General/SSL cert verification
  2. Used settings/proxy (Use System Proxy)

and in all cases I done settings for SSL certificate Verification (off)

and I still get:

Could not get any response
There was an error connecting to https://epicorapp2/ERP10.1Test/api/v1/Erp.BO.JobEntrySvc/JobEntries?%2524top=1.
Why this might have happened:
The server couldn't send a response:
Ensure that the backend is working properly
Self-signed SSL certificates are being blocked:
Fix this by turning off 'SSL certificate verification' in Settings > General
Proxy configured incorrectly
Ensure that proxy is configured correctly in Settings > Proxy
Request timeout:
Change request timeout in Settings > General

But what is working oddly enough is if I turn on Fiddler v4 and then I see traffic both in fiddler and in postman.

So what am I not configuring properly?

Full request contents:

GET /ERP10.1Test/api/v1/Erp.BO.JobEntrySvc/JobEntries?%24top=1 HTTP/1.1
Host: epicorapp2
Authorization: Basic eXNnNDIwNjp5ZWNoZXprYWw=
cache-control: no-cache
Postman-Token: d1a57676-8381-4eed-bb6e-c1bb61888faf

1 Answers

Mihai Albert On Best Solutions

There is a setting called "Automatically Authenticate" within Fiddler with will automatically use the credentials of the current user to do NTLM/Kerberos authentication when required. If it's ticked in your config, it might offer a hint about why it's working:

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Just to make sure it's not a quirk within Postman, try a different REST client, such as Insomnia, and see if you get the same outcome (I personally had to move to this one from Postman, since it could successfully do NTLM authentication). It supports proxies so you should be good.