Exchange ActiveSync Search command is very slow

Hi,

I am using the ActiveSync Search command as shown below.

<?xml version="1.0" encoding="utf-8"?><Search xmlns="Search" xmlns:airsync="AirSync"><Store><Name>Mailbox</Name><Query><And><airsync:CollectionId>7</airsync:CollectionId><FreeText>Presentation</FreeText></And></Query><Options><RebuildResults /><Range>0-4</Range><DeepTraversal/></Options></Store></Search>
For certain mailboxes, the above search takes 30-120 seconds. In some cases, the HTTP Client time-out, or leads to a Status Code 10 (Timeout occurred). Are there ways to speed up the search? Does it depend on size of the mailbox?
Thanks