It all began after the update to Thunderbird 45.40 To be more accurate - When I try to open a message in conversation, I see a new tab with the search logo on top searching for a different message's subject - and without showing any results. let's say I have a thread consists of 5-6 emails on the same subject, and I want to see those emails in conversation view (which was great until the recent update) - I used to right-click one of those emails select " open a message in conversation". What happens now is that I right-click -> " open a message in conversation" and I get different search results in the search tab that opens for each of the messages in the thread... none of those searches is relevant or related to the subject of the original message, but it searches a subject taken from a random old message from my inbox.