The problem is, that most clients do not download the full email, just the headers. The e-mail is downloaded and displayed when you click on it.
As I discovered during a five hour internet outage here last Saturday, you cannot read or edit e-mail, because it is stored on the web server. No internet, no e-mail.
Download ALL Mail Content Using IMAP
The answer is to set your client to download the full e-mail, not just the headers. On this computer I am using Outlook 2003. Here is how to set it to download the full text of your email.
Note that my mail is stored on Gmail.
Go to: Tools > Send / Receive > Send / Receive Settings > Define Send / Receive Groups
or type <Control + Alt + S.>
This dialog box appears:
Tick the folders you want to download & Save.
Contents will then downloaded to local storage and be available offline.
Done! All e-mail should now be available offline, and be updated / syncronised when connected.