Brackets in an address name seem to confuse the importer. CASE ONE If the To line in Eudora is the following: To: John [@home] Doe Then post-import, the To line in Thunderbird is, To: "@home] Doe Note that the last address is missing characters at the beginning and its closing quote ("). Both lines are from the mbox source, not the UI. It also happens if there is more than one address on the line. CASE TWO In the same mailbox, I have an email sent to 45 addresses. The 37th address is: John [@home] Doe. (Same address as in Case One.) It imports as only a double quote ("), and the list of addresses is truncated there -- addressses 38-45 are missing. NOTES That seems to happen other times when the address with "[@", including Jane [@ work] Doe.
Importing from Eudora was removed from Thunderbird in bug 1243498. Please see http://kb.mozillazine.org/Importing_from_Eudora_-_Thunderbird on how you can still import from Eudora if you need that.