I think migrating from XP to Windows 7 is a big mistake, as Win7 is essentially an even more bloated version Vista with most of the bugs removed. If you seriously want to upgrade to a more current OS, switch over to Debian with the GNOME Desktop. There you will have an email program called Evolution which is essentially an Outlook work alike.
That being said, the directory structure is ENTIRELY different from Window, and you will have to take some time to learn how it works, as well as some minor Desktop and configuration issues that are completely different from Windows. --If you have an ATI or NVidia graphics card in your system, you will also need to set your system up to use proprietary software archives to get the proprietary XServers and driver/Kernel modules in order to get the proper graphics acceleration.
That being said, once this is out of the way it's a better system than Win7, provided that you are not a serious gamer.
To save your emails though, you will most likely have to save them individually as text files, and make a directory to store them in, rather than move them to another program. --You will have to face the same issue even if you migrate your system to Windows 7.
Personally, I haven't touched an Email client in since 2004, and have absolutely no issues with using Web Based Email like GMail and others as it is generally more secure than using a POP3 client.
_________________
When There's No There to get to, I'm so There!