The attempted operation is prohibited because it exceeds the list view threshold enforced by the administrator (GetListItems = 350)
If you are experiencing the above error when trying to ‘Search Tickets’ or access ‘My Tickets’ panel under Outlook > Issue Tracker toolbar > My Options, this is an indication that the number of items in that particular SharePoint list has exceeded the default threshold limit set by your administrator for one time database operation.
NOTE (VERY IMPORTANT) for Office 365 SharePoint Online Users: If you are getting this error from a SharePoint list that is hosted on Office 365 Cloud (eg. SharePoint Online), there is NO workaround (as of the writing of this KB article). Because Microsoft has fixed the threshold limit to 5000 only and has not provided the option to change the List view Threshold of SharePoint lists. So if you are using Office 365 SharePoint Online, and if the total items in your old SharePoint list is about to cross or exceeds 5000 threshold limit, the only solution is to add new a SharePoint list (in Outlook > Issue Tracker toolbar > Team Settings > Configure SharePoint Ticket lists) so that you and your other team mates can use the new list to store the tickets henceforth. (and performing the same cycle once a SharePoint list exceeds 5000 items)
Workaround for On-Premise SharePoint users:
The solution is to raised the default threshold limits to higher value. The steps below should be performed by the SharePoint administrator.
1- Login to SharePoint Central Administration.
2- Go to Application Management -> Manage Web Applications.
3- Pick the Web application for which you want to change the List View Threshold.
4- In the ribbon above, click General Settings. That will bring down a menu, from which you should pick ‘Resource Throttling‘
5- Change the List View Threshold (first item in this list) to another value (say 20000) and press OK!
NOTE: The error ‘Microsoft.SharePoint.SoapServer.SoapServerException‘ (Exception Number: 5) has no effect on the ability for Issue Tracker add-in to raise new tickets from Outlook to the particular SharePoint list (with the List View Threshold exceeding issue). The threshold limit comes into affect when the Issue Tracker add-in tries to read through all your existing ticket items in that particular SharePoint list (such as when searching tickets ‘Search Tickets’ or ‘My Tickets’ panels in the addin).