If you are finally ready to move from Eudora to Thunderbird, here are some tips from my experience today (a close relative had been notified that authentication would be required in the future, a feature not available in Endora.). Here are the steps I took: # First, do NOT install a current release of Thunderbird. It doesn’t have the required conversion tool. The import tool is on an earlier version of Thunderbird, probably not available after release 31 or thereabouts. I used release 17.0.9 for this and it worked well. https://ftp.mozilla.org/pub/thunderbird/releases/17.0.9esr/win32/en-US/ # Eudora needs to be installed, and the import feature will do its thing. The import process will import the addressbook and all message folders. Although the messages were all captured, the addressbook import mangled content other than email addresses (such as phone numbers and postal addresses). # Do NOT use the resulting profile, even though you may feel the work is done. It is not. This is because Thunderbird has evolved since that old release of 17.0.9 happened and much has changed. Instead , do this: #* Exit thunderbird #* Copy the ...appdata\thunderbird folder elsewhere for safekeeping (that folder is at c:\users\<yourid>\appdata\roaming\thunderbird.) #* uninstall this old version of thunderbird and delete the default appdata\thunderbird folder #* install the current release of thunderbird #* set up the email accounts. If POP, do NOT enter password to ensure no messages download in the interim. #* exit thunderbird and, using Windows File Explorer, copy ALL message folders and files from the 17.0.9 profile’s imapmail or mail folder to the new profile’s imapmail or mail folder as appropriate in same location within profile, e.g., Mail\<accountname>\<all message folders and files> - this is important only for POP, as IMAP mail will autopopulate. #* click the Tools>import>Import from a file menu to import the MAB addressbook (abook.mab and history.mab) from the 17.0.9 profile. There will be errors to delete if the old addressbook including phone numbers or postal addresses, but otherwise it works. # Now, do a backup for safety, exiting Thunderbird first.