One of my users outlook 2010 machines was running awfully slow, hanging and sometimes crashed today. In the end i removed all the files from c:\users\user\appdata\local\microsoft\outlook\ and fired outlook online again to recreate the files. This old ost file was 9.5gb, the new one is 4gb.
What reason has it stayed so large. Her mailbox was 2.5gb and another shared mailbox was 2gb.
Does the ost files compresses itself automatically?