Accessing your IMAP account from your mail client of choice is usually a simple matter of adding a new account to access for mail, selecting the IMAP protocol, specifying your server's address, and your login and password to the IMAP server. You may then need to subscribe to some or all of your IMAP folders, depending on the client in question.
In Mozilla Thunderbird 0.8, but not necessarily on more recent versions, select Tools and then Account Settings. From there, Add Account..., choose Email account, then follow the wizard through until you get to the Server Information window. Select IMAP and enter your IMAP server's IP or hostname. Finish. Now, select the Server Settings entry for your newly created account. Click Use secure connection (SSL) to enable SSL. Next, click on the Advanced... button. For your IMAP server directory enter "INBOX/" without the quotes. This will ensure your folder hierarchy is displayed properly. Hit OK to complete setting up your new IMAP account.
In Kmail v1.7 and above, choose Settings and Configure KMail and then select the Network icon. Switch to the Receiving tab and then Add... to add a new account. Select the IMAP radio button. Now, enter a name for this account, a username, password, and your IMAP server's IP or hostname. Next, enter "INBOX", without the double quotes, as your Prefix to folders. This ensures that your folder hierarchy is displayed correctly and you can add, modify, and remove folders without errors. From there, select the Security tab and click See What the Server Supports. KMail should respond with two warnings about the invalidity of your X.509 certificate. Accept the certificate anyway and tell it to use it forever, or for this session. Your choice. KMail should then finish determining what the server supports and should now have Use TLS for secure mail download selected by default. You're done, hit OK. (Earlier versions of KMail may decide to use SSL instead of TLS.)
In OutLook Express v5.5, select the Tools menu, then select Accounts. Now, select the Mail tab and click on Add. Select Mail... and go through the wizard until you come to the E-mail Server Names section. Here you'll want to enter the IP or hostname of your IMAP server and select IMAP as the server type. For Internet Mail Logon, leave the Secure Password Authentication box unchecked as you will not be using this. Finish, then select your new account from the list under the Mail tab and select Properties. Select the IMAP tab and make sure you enter "Inbox" as your Root folder path without the double quotes. Then, go to the Advanced tab and check This server requires a secure connection (SSL) for your incoming mail server. This is important so the folder hierarchy shows up correctly. If you ever modify, add or delete folders from another IMAP client, you'll need to select Reset List for your account by right clicking on it in OutLook Express' main window.
For SquirrelMail 1.4.3a, you will want to edit your /etc/squirrelmail/config.php configuration file so it knows you are using Courier IMAP. Set $imap_server_type to courier. While SquirrelMail does not support SSL directly for accessing your IMAP server, if your Web server is running on a different machine, you can make use of either an OpenSSH tunnel or stunnel to ensure your IMAP sessions are fully secured. The WiKi for SquirrelMail has complete details on how best to setup SquirrelMail to speak SSL.
As you read through the above, you should have picked up on the "INBOX" theme. While an extension to the IMAP protocol announces this prefix, the above clients don't bother to use it. So you need to enter it manually. It's possible other clients not discussed here will pick up on this automagically, but if not search out the prefix or server directory option for your favorite client and add some variant of inbox there. The client might want it in a specific case or with a trailing slash, or it might convert it to its desired scheme after you save your changes.