Step 1: Open Outlook and go to Tools –> Options.
Step 2: Click on the Mail Setup tab, if you want to disable automatic sending of messages, just uncheck the box next to “Send Immediately when connected”, this will disable automatic sending of messages.
Step 3: Click on the Send/Receive button in the same tab, this will open a new options window. To disable automatic send/receive for your account group, just select the group from the list and uncheck the box next to “Schedule an automatic send/receive every”.
With the automatic send/receive disable you will still have to download emails, just press the F9 key with the Outlook window in focus, whenever you want to manually send/receive email in Outlook.