I have installed Thunderbird and the Import/Export tools. I am changing email accounts and I need a way to download existing emails and attachments to an external hard drive so that I may access them at a later time. I followed the directions and began downloading my email, but it stopped saving emails after about 5000 of my 39000 emails. The program is continuing to tell me that it is slowly downloading, but it is no longer writing to the external hard drive.

Where are the emails going? How can I get them later?