Just note that fastmail‘s search is basically useless if you expect Gmail-like search (unless I am missing some sort of trick to get it working). The rest of Fastmail is excellent though.
I use thunderbird IMAP and honestly, the search is not great either.
If I have trouble finding something, recoll normally does the job. It indexes thunderbird too. And should you have a ZIP attachement in thunderbird, it will index the content too. :-). I think you could even set up up with cuneiform that a PDF inside the ZIP attachment goes through OCR should it not be plain text.
(I work for Fastmail). Our search is comparable and in some ways more powerful than Gmail's search. If you're having problems, please create a support ticket (or just email support@fastmail.com) and we'd love to look into that for you. Thanks!
Can’t say I’ve had many issues with Fastmail search at all. Google is known for search so they would naturally prevail for some searches, but Fastmail does just fine.
https://www.lesbonscomptes.com/recoll/pages/index-recoll.htm...