There is no Mozilla Thunderbird server. Why did you think there might be? Thunderbird is a mail client which works with a server provided or operated by your email provider. Mozilla is not a mail provider. If an account is set up to use IMAP then messages in that account will by default be stored "in the cloud", i.e. on that IMAP-connected server. If you don't want your stuff on the server, Thunderbird provides a "Local Folders" account which stores messages on the local system storage, usually your hard drive. If your email account uses POP, then it downloads all messages to your hard disk. In this case, Thunderbird can be set to leave copies on the server, so you may choose to check this setting and ensure it is set as you want. You said you want to ''move'' your messages, so after this download, they should no longer be on the company Exchange server. But you'll presumably still need to connect to the Exchange server to receive your works email messages? I use Thunderbird myself on an Exchange server, mainly to avoid using Outlook. I need to use Davmail to interface TB to Exchange. This makes Exchange look like an IMAP server and I set TB to move messages on receipt to Local Folders, to make sure I have local copies on my laptop that can be taken with me when I work from outside the office.