Speeding up the message sync between Outlook and your email host.
Outlook’s default action for IMAP accounts is to download the message header only; you have to mark the message for full download. That was probably a good idea when dial-up modems ruled the earth but is more of a nuisance now. Most people will want and expect Outlook to fully copy messages to local storage for faster and offline access.
To do that go to Tools | Send/Receive | Send/Receive Settings | Define Send/Receive groups then choose the main Send/Receive group (you may only have one ‘All Accounts’ – select it).
Click on the Edit button then select the IMAP account from the list on the left.
Ensure that the account is set for downloading complete items including attachments.
Using Headers download only
If you decide to only download message headers and mark messages for individual download to Outlook you need to be aware of some limitations. When using IMAP in online mode, the mails are located in the server, but the mail client does not copy the entire message at once and then delete it from the server. It is like an interactive session between the client and server where the client asks the server for parts of messages like headers or bodies of certain messages.
The user has the option of storing the entire message in the local system or on the server or both. But when you are viewing messages that have only headers downloaded you cannot view the body of the message unless you download the body of the message also. Likewise if you have any rules set up to act on text in the body of a message, it will again not work for IMAP messages that have only headers downloaded.
Even for this the entire message need to be downloaded (A rule is a certain condition which you specify for a message and Outlook takes the action which the rule specifies on an incoming or sent message. Rules are applicable only on unread messages).
It is not recommended to download huge messages from the server as IMAP clients are found to crash at times due to the load. However that should not (fingers crossed) be a problem with recent versions of Outlook.
