There are numerous articles on the topic of RPC latency on the server and the RPC Dialog box "Outlook is retrieving data from the server...", but there is one cause I don't see mentioned in some of them. Keep in mind that this is only one possible cause of many, but I have had a couple of customers lately for whom this resolved the issue. In these recent cases a single calendar item was causing delays when it was accessed. In both instances the calendar item was quite large. One of the meetings was a long running recurring meeting with no end date that had been edited many, many times over several years. The meeting had grown to over 500MB in size. Giving the meeting an end date didn't mitigate any of the problems.
We found the meeting by:
- open the user’s mailbox in Outlook
- go to the calendar
- display the calendar as a table (go to the View tab, select Change View from the ribbon and then select List view)
- sort the calendar by size (you may have to add the Size field – Select View Settings, click the Columns button, select “All Mail Fields” and then add the Size field to the display)
- look for any items that are abnormally large
Once we had found the largest meetings we moved them to a PST file. In these cases there were relatively few large meetings. We moved them one at a time to a PST file and tested to see if there had been any impact on the symptoms. In each case moving one of the large meetings out of the mailbox eliminated the issues the client was seeing. Once we knew which meetings were involved we had two choices. We could recreate the meeting or we could attempt to diagnose the precise problem with the meeting we moved out. In both case we elected to simply recreate the meeting because it involved the least administrative effort.