Outlook 2013, Exchange 2013 and Sharepoint 2013 not synchronizing Tasks.

I have set up SharePoint and Project server 2013, we upgraded to exchange 2013 from 2010 about 3 months ago, I have set up the prerequisites for task synchronizations, ran all the commands and program synced them together. When I try to synchronize with outlook I get the following error sharepoint, project and mysites:

"We weren't able to sync your tasks. This could be because your mailbox is on an Exchange server that isn't supported for syncing tasks. Please contact your administrator for more help."

At this point I am not familiar enough with SharePoint to even begin troubleshooting where to start with an extremely vague error. I looked in the logs (C:\Program files\Common Files\Microsoft Shared\Web Server Extensions\15\LOGS and event viewer) I don't see anything to point me in the right direction.
 a few sites said that you need to use the server name for the exchange server (exchangeservername.domain.com) and not an alias(mail.domain.com), I set that up and got the same thing. they also said to check that there are not two IP's registering in DNS for that server name. I only have one IP in my DNS internally mail is a static a record to the same ip as the server. Someone said the certificate could be causing it by not having the correct names but both the server name and the alias is on the cert. Does anyone know where I can look to see if what the problem is or how to tell?

*** EDIT ***
I would also like to say that this sharepoint and project server was upgraded from 2010 to 2013.
Also all sites are upgraded to 2013, nothing is runnning in 2010 mode.
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Shailaja KumarCommented:
If this is not yet resolved, you can follow the below article to get an idea,
Crossroads305Author Commented:
Hi Shailaja, I have tried all that, going through the ULS Logs looking at the correlation ID doesn't show anything of use. I have set up the exchange and sharepoint servers exactly as how the documents show.
Crossroads305Author Commented:
So I seemed to have it tracked down to that some users are getting 2 profiles, the ones that had the error had 2 I deleted the rouge one and then it started syncing in outlook.
now im just trying to figure out how they are getting 2 profiles

Our domain is named domainnet yet we log in with domain\username which is the pre2000 name

only certain people are getting two profiles and one will show up as domainnet\username and the second one as domain\username this also only seems to happen after the user profile sync happens.

once I delete the domainnet\username profile the problem goes away and they sync fine to the task in outlook. if this user profile is there the tasks don't sync, have you ever seen this problem before with sharepoint and user profile syncing? and is there a way to tell it to sync domain\username and not domainnet\username?

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Crossroads305Author Commented:
This solved the issue by removing the duplicate profiles in sharepoint.
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