Doesnt work with local Exchange server

Have tried everything including spending a good fifteen minutes with our companys sysadmin to get this to work. Tried to talk to the developper about it.
1 - Online chat was rude
2 - When sending a transcript of the chat to the developper, I had no answer.
3 - Trying to communicate with the developper to no avail.
Heres a transcript of the chat :
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Hi, Im at a loss... I bought Airmail for work. Have installed it on all my devices. But with the Mac at work, it wont connect to the Exchange server. I keep getting an "Authentication needed" message.

10m ago
paul-1461582424.jpg
Hello!

Does your account is EWS supportedd?

Please follow these steps

Open the endpoint in safari.
You will be prompted to enter login and enter credentials.
If you can login there, you can login in Airmail too.
This is due to the fact that we only support Exchange that are EWS enabled.

The endpoint URL can be asked by you from the service provider of your email service.

7m ago
I dont know if its "endpoint" enabled. The web address to access the server ends in /owa/. However if I check the OS X Mail settings under the Advanced tab, it shows an news/exchange.asmx address.

4m ago. Seen.
paul-1461582424.jpg
Please ask your service provider about it, thanks.

4m ago
Sorry ?... Is that all ? I was sysadmin for over 150 Macs a few years back. I have spent 15 minutes with the actual sysadmin of our network and couldnt get it to work.

2m ago. Not seen yet.

I have made a copy of this conversation. And will be demanding a refund for the licences I bought. Thanks.
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MachinChose about Airmail - Lightning Fast Email, v3.0