Ian Grieve delves into an Exchange login issue.
Microsoft Dynamics GP 2015 R2 user cannot login into Exchange – azurecurve
— Read on www.azurecurve.co.uk/2020/04/microsoft-dynamics-gp-2015-r2-user-cannot-login-into-exchange/
Microsoft Dynamics GP 2015 R2 user cannot login into Exchange – azurecurve
Install, Upgrade & AdminGP 2015
Archived post from 2020. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.