For the past two years I’ve been using Thunderbird to receive my mail from various webmail services. I used to like the security of a mail client as it allowed me to keep a copy of my emails online and another copy on my PC. Recently though, I’ve decided to ditch Thunderbird and only use Gmail. I set it up so all my other webmails would redirect to it and recreated the same labels I had in Thunderbird. I was a bit disappointed to find that there was no easy way of exporting filters from Thunderbird to Gmail but was happy to find that you can export back old email into Gmail.
Google Gmail Loader (GML) is a GPL application created by Mark Lyon, which reads existing email and loads them back into Gmail. In the interface all you have to do is enter your Gmail username and password, configure your email file by selecting file type (in my case, mBox, which is used by Thunderbird) and if you want files received or sent. This application is a godsend if like me you have lots of old email stored somewhere on your hard drive and want to be able to browse them easily online.