I had, a long time ago, a non-free email account. Once I opened a Gmail account I forgot about it, but I still have all the emails stored (in Thunderbird format).
I would like to be able to join them with my current Gmail account, as it is always difficult to search for old emails. The ideal will be keeping the fields like
Cc, etc, but just forwarding everything to Gmail could be enough.
I'm talking of about 700Mb of information.