When coupled with IMAP, thunderbird is just great.. But, it has its drawbacks as well and can be addressed with slight tweaks to the settings. I will list down some tweaks and settings to the basic installation that makes thunderbird a competition to MS Outlook.
Thunderbird doesn't have a calender by default. So, it can not handle Appointments and schedules by default. To overcome this, we have to install an add-on called Lightning. This is also developed by Mozilla corporation and it integrates into thunderbird very well.
Most of the people use outlook in a minimized status to save space on their taskbar. Thunderbird can achieve this by installing an add-on called Minimize to tray.
Thunderbird adds the previous mail content as a quote and the cursor is positioned at the bottom when replying any mail. This is bit uneasy as we have to always press "Ctrl + Home" to go to the start of the mail before writing anything. To tweak this, follow the steps mentioned below:
1. In Thunderbird: Go to "Edit > Account Settings" *
2. Select "Composition & Addressing" for the account in question
3. Make sure the "Automatically quote the original message when replying" checkbox is checked.
4. In the drop-down box below that, select the option "start my reply above the quote"
* On Windows, the option can be found in: Tools -> Account Settings.