There are many factors that contribute to the speed of synchronization between Microsoft Dynamics CRM Online for Outlook and Microsoft Dynamics CRM Online.
Initial synchronization is typically slow because you are copying data to your computer. The speed of subsequent synchronization depends on the amount of data that you are synchronizing. Later synchronizations are faster because only changes and additions are being synchronized. The best strategy for speedier synchronization is to reduce the amount of data. Here are a few suggestions that might help speed up synchronization:
After you have completed one or more of these suggestions, perform a synchronization. Note that the first synchronization performed after one of these steps will still be slow because records are being removed from the local data store. However, subsequent synchronization should be faster.