I think the error (the long error that starts with with "The server response was: 5.2.0") is caused by the fact that the Sender Email does not have permission to send email to the cloud-based email server. I sent an email to the customer to check on that but since he has life and off during the weekends, I won't hear from him until Monday.

Interesting that I have ASP.NET application - on the same server - that has nothing to do with your product. And I get the same error when the ASP.NET sends email too. And the Sender Email is the same. So, I presume - I don't know for sure - that this is the problem.

Strange issue, however, in the ASP.NET app. When I specify the server name with the port number (SmtpClient("smtp.office365.com:587"), the error message simply says "Failure sending email". However, if I remove the port number from the email server name ("SmtpClient("smtp.office365.com") and set the port 587 using the .port property, as (client.port = 587), I get this long error message that starts with "The server response was: 5.2.0".

>That's because you're likely loading the DLLs from a non-local or mapped drive. In Remote Desktop that might be any non-root drive perhaps - i don't know but the LoadRemoteSources just makes .NET behave like any other Win32 application when it comes to loading resources of non-local drives. The load error is completely different than the SMTP error you are getting **from your server**.
>
>IOW, wwSMTP is working and sending the email but your server is refusing the message. There's not enough info to see why, but the message is getting to the server and the server sends back a denied message. Either you didn't provide the right credentials or you're not on an allowed senders list (if using a corp server that's very likely)
>
>To be safe always try to send a message through a known good email server that uses the same protocol settings. Gmail, outlook.com etc. all work fine so that's the first avenue to check. Then try with your mail server and make sure you know what the rules are to connect to and send via that mail server.
>
>+++ Rick ---
>
>
>
>>To add to my previous message.
>>The error, long error that start with Transaction Failed. The server response was: 5.2.0 pops only when I use the MyApp.exe config with the following line:
>>

>><loadFromRemoteSources enabled="true"/>
>>

>>
>>If I set the above line to the enabled="false" or remove the .config, I get the error:
>>

>>Unable to load wwDotNetBridge: unable to load Clr Instance: 0x80131515
>>

>>
>>>I don't think you are running the right SMTP component? It says something about MAPI in the error message which the .NET component should not be using unless there's some special system configuration.
>>>
>>>+++ Rick ---
>>>
>>>>I just added myapp.exe.config and now I am getting a different error (please see attached image).
>>>>What do you think?
>>>>
>>>>>Naomi's issue was likely different that what you're looking at. For her it was finding the right EXE to add the .config file to (the launching EXE) that allows access of the wwDotnetBridge.dll over a network.
>>>>>
>>>>>To troubleshoot this start with the files locally (not on a network drive) and making sure the file is unblocked.
>>>>>
>>>>>There is more information in this help topic:
>>>>>
>>>>>Unable to load CLR Error in wwDotnetBridge
>>>>>
>>>>>
>>>>>+++ Rick ---
>>>>>
>>>>>>>>>In my own solution I just upgraded to the very latest version of Newtonsoft.Json.dll file which is version 11.02. However, I have lots of places where different versions of this dll are installed. I'm not sure where this particular version is coming from and what should I do to resolve this issue. Found a few threads on Stackoverlow with the same issue - sounds like I'm in the dll hell now.
>>>>>>>>
>>>>>>>>I suggest that you ask your question at https://support.west-wind.com/
>>>>>>>
>>>>>>>Thanks, Tore. Added a new question
>>>>>>>
>>>>>>>https://support.west-wind.com/Thread5AQ0B5KBT.wwt?rl=1#5AQ0B5KBU
>>>>>>>
>>>>>>>It is a big showstopper for me - I need to resolve it ASAP :(
>>>>>>
>>>>>>I saw your thread on .west-wind.com. I am having kind of the same problem with the wwDotNetBridge. But I don't use Newtonsoft.Json.dll.
>>>>>>Was your solution tied to this dll?
>>>>>>What was the solution?