Today, i upgraded my KDE installation to the latest version, KDE SC 4.6.4. This version also brings a new KDEPIM package along with Kontact which is now based on Akonadi framework. I used KMail a lot in the past to manage my email, so i decided to try this new package.
After upgrading, i tested the new KMail by registering my account to KMail and it instantly checked my email using IMAP protocol. So far so good. The problem came when i started to read the messages. Sometimes, it's not really synced properly, so even if i deleted the message, it's still there, or sometimes it displays the wrong message for me. KMail also support OpenPGP/S-MIME by default, so no addon is required to have signing/encryption feature enabled.
Next, i tried Thunderbird to do the same thing. It actually gives better performance over KMail, but it does require an addon (enigmail) to work with OpenPGP/S-MIME. Spam detection are included in KMail, but we must install AdBlockPlus for Thunderbird, but so far, i'm quite satisfied with it, so not a big problem for me.
At last, i decided to stay with web-based interface, meaning i abandoned all those two applications, since my email has lots lots of email and it would be problematic for me to sync all of them. So far, i managed to reduced a lot of my email by deleting the old and unused threads on my inbox, but still there are 2 GBs of email which is still considered important for now and i don't want to delete them. Syncing 2 GB is not a good option if you have slow Internet connection.
So, probably i will leave IMAP for now, until i have much better Internet connection