However, after some persistent work by a few MVPs working with Microsoft support, it seems the cause of the unexpected Outlook authentication prompts has finally been identified as a bug with Outlook itself.
But all signs pointed to an issue with MAPIHttp. MAPIHttp is the future, so it really needs to work. RPC-over-HTTP has been deprecated, so we can expect it to go away at some stage in the future. It’s not ideal to be turning off MAPIHttp in production environments. Unfortunately, what we discovered was that disabling MAPIHttp made the Outlook auth prompts go away completely. MAPIHttp is the protocol that replaces Outlook Anywhere (RPC-over-HTTP) for Exchange Online, and optionally for Exchange 20 on-premises environments. But the intermittent nature meant that customers were often reluctant to continue to engage a consultant to troubleshoot the issue, or to open a case with Microsoft, and so visibility of the issues were lost.Īfter lengthy discussion and testing in various environments to try and reliable reproduce the issue, we began to narrow it down to a potential problem with MAPI-over-HTTP (or MAPIHttp). Several other MVPs had also seen the issues at their customers. Kerberos authentication had been deployed/removedĪnd yet the random, unexpected authentication prompts continued.Īfter seeing these issues for some time, I recently learned that I was not alone.Individual Exchange servers had been excluded from client connectivity.Sufficient time had passed for any Autodiscover caching on servers to have expired.The virtual directory settings on servers had not been incorrectly modified.The namespace and SSL certificate configurations were correct.It’s difficult to write this article without going into a long list of possible causes of authentication prompts in Outlook, but in the cases I had looked at: For a domain-joined computer running Outlook and connecting to Exchange, authentication prompts should be non-existent, assuming everything is configured correctly. But every now and then I’ll encounter an intermittent issue with users reporting unexpected Outlook authentication prompts. My build process is fairly well refined, and avoids common issues like incorrect namespace configuration or invalid SSL certificates. I build a lot of Exchange environments – for customers, for testing, for training courses.
0 kommentar(er)
