Outlook 2010 Calendar reminders not working anymore in a Citrix environment.

Recently we encountered the problem that one of our customers weren’t getting any calendar reminder pop-ups. As there were only a few people that had this problem we had to figure out what was causing this.

After trying al of the traditional solutions like a profile reset and different servers etc, we had to look at it from a different angle.
First do the reminders work on a non-Citrix computer? It turned out that they do!

So we fired up an old computer where we installed the mailbox of the people that had this problem. After a minute we got the reminders popping up! But then we encountered the next problem, there were missing reminders!

There should have been loads of old reminders from several weeks back that weren’t reminded. So then we de-installed Office 2010 and installed Office 2003.
In Outlook 2003 it took 5 minutes but then came the reminder box, 790 reminders…

Lets first clean that up! We brought that back to 30 reminders, by removing all that were older than 1 week. Let’s test it!

Unfortunately still no reminders coming up .
Back to the bat mobile, old computer!  Maybe there is still something in the background of the mailbox blocking it.  After doing some research we open a dos-box.  There we went to the Office directory in c:\program files\Microsoft office\office 11\ and ran the following switches:

Outlook.exe /clearreminders
Outlook.exe /cleanfreebusy
Outlook.exe /resetfolders

While we ran this commands on the other computer with the mailbox still open in Outlook 2010 within Citrix the reminders popped up!

After double checking it, we got reports of the costumers that it was indeed working again!

What was causing it? At this point we think that this was caused because of the following:

1. The hundreds of old calendar items still in the calendar.
2. After cleaning it apparently the counter still had to be reset so outlook
would also know that the reminders were gone.