Here is a quick blog for those of you setting up server side sync in Dynamics CRM: If your Email Server Profile is set to "Credentials specified by a user or queue" as shown below:

Then the incoming "Email Configuration Test" for a mailbox does not check the credentials access to the email address specified. As long as the credentials entered have access to the Server specified in your Email Server Profile, the test will succeed, regardless of whether those credentials can open the mailbox, or if the mailbox even lives on this server.
In the example below, the email address is not valid (PowerObjects is misspelled) yet the Incoming Email Status shows "Succeeded".

This is a good reminder to always double-check your email addresses and credentials when configuring or testing Server-Side Sync, even if your Configuration Test results are a success. If you are switching from an email router to server side sync in Dynamics CRM, click on the link for a super great and informative blog that will get you up and running! And as always, if you run into trouble, we are happy to help! You can reach out to us here.
Happy CRM'ing!
Ever run into a situation where the Email config test is scheduled, but never acutally runs?
Having the same issue- any advice would be appreciated. I already tried restarting the Async services.
Same issue after upgrading from CRM 2013 to 2015
Hi - The two most common issues we see are when the encryption keky is not defined. And when ssl is not supported and crm still set to enforce SSL. http://crmbook.powerobjects.com/system-administration/server-side-sync/common-problems/
The other item to check - if your crm is on premises and you have a service account for your sandbox service, do you have an SPN? if not, this could be part of the issue.