With the current Search it does not allow searching of any content in the body of e-mails and/or attachments.

Can you please make this work at least as well as Apple Mail Search if not better?

When searching through your mail, only exact matches for terms are returned. This is unhelpful when you know the topic of an email but cannot remember the exact terms used.
For example I recently use the term "democratic review" when what I should have entered was "democracy review".
It would save time and be more useful if the search function could also act to search for related similar terms.
Perhaps allowing to search using boolean operators would also be advantageous, as then I could manually decide to search for ("democra* review") which would return any results where the first word started with 'democra' and the second word was 'review'.

I like Protonmail, but the search bar is terrible. Even when I set its search parameters to "all" it appears to still only search the text in the subject lines of emails, and not the full text of the actual emails. I have a Gmail account that forwards to Protonmail, and the Gmail search bar always returns comprehensive results and shows what I'm looking for. With Protonmail, I sometimes can't ever find what I'm looking for because I can't remember the exact wording of the subject line of an email. The thing is, a search function that searches the full text of emails shouldn't even be that hard to add to Protonmail. It's a simple word search in a relatively small pool of data. You could probably find the code on Stack Overflow! I pay $5 a month for Protonmail, and I'm happy to do it. But when I see that Protonmail doesn't even have a decent search bar like so many free email services do, I am honestly baffled.