User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:52.0) Gecko/20100101 Firefox/52.0 Build ID: 20171005074949 Steps to reproduce: Open Thunderbird, (It is configured for unified inbox with Gmail, Icloud, and Yahoo mails) Actual results: The list of emails shows some emails in 2 adjacent repeated rows. such emails cant be deleted. but the header becomes blank in the list of emails. Expected results: The mail header listed only once for each mail. The mails must be deletable by selecting the header in the list of emails and clicking the delete button.