Hello Community!

Recently we have seen some cases come in with users getting the following error whenever they attempt to email after upgrading to GP 18.3 (either 18.3.1173 or 18.3.1200):

                                                              

The Unknown Error message is used when GP is not sure why the process failed. Usually this comes down to the odd things like unexpected characters in emails.

For these new updates, however, we have noticed that another cause has cropped up, Exchange itself.

For GP 18.3 we started using a new Exchange process to allow for TLS 1.2 and MFA. This process uses new code that works awesome, but it uses code that was designed with Exchange 2013 and newer in mind.

For all versions of Exchange past 2013, this process works great and emails send without a problem.

For Exchange versions prior to and including 2010, the process will not work in any way.

To confirm what version of Exchange you are using, you can do the following if you have Outlook installed. If you do not have Outlook, then you will want to ask your IT team for the version of Exchange being used:

  1. Hold Control on your keyboard and right click on the Outlook icon in the icon tray (bottom right in Windows)
  2. From the menu that appears, select Connection Status
  3. In the Connection Status window there will be a few emails listed (depending on how many you use), the version can be found all the way to the right:

Only versions starting with 15 will work with GP. Exchange 2010, for example, starts with 14. 

More on this process can be found here:
Determine the version of Microsoft Exchange Server my account connects to - Outlook

If you are seeing versions of 14, then you will want to investigate upgrading Exchange. At this time GP will no longer work with Exchange 2010 as it is no longer supported by that team:
Exchange 2010 end of support roadmap - Microsoft 365 Enterprise | Microsoft Docs

In the meantime, the only workaround is to use 32 bit Outlook with MAPI or a basic O365 account to email.

If you are seeing all versions of 15 or higher, then your issue may come down to one of the other causes of this issue outlined in the Email Troubleshooting Guide here:
Dynamics GP Email Troubleshooting Guide - Microsoft Dynamics GP Community

Hopefully this saves everyone some time and headache.

Happy Emailing and Happy Holidays!