Labels should be distinct from folders/inbox/archive so it can be combined.
eg., "label:bank in:archive is:starred"

Right now, you can search a label, but you can only do so if you use the label in place of those other two, not combined. If you're going to compete with gmail, having excellent (let alone passable) search is critical.

This is available at least in desktop website version. Click search field, then 'other' under "search in" in the dropdown. It lets you pick what folders & filters to search in.

The search term must be highlighted (e.g. yellow as in other search engines)

I'd like to be able to search emails with attached files (or without attached files)

Hi. You should compile a dictionary of every email content to provide a client side search like mkdocs. All the processing can be done client side. The dictionnary can then be stored encrypted on your side. https://squidfunk.github.io/mkdocs-material/setup/setting-up-site-search/

You should also implement openid and connect your forum with it and try to block spam. Proton OpenID should be available to authenticate all app on the Internet that wish to use it.

The search on iOS is pretty trash compared to Apple Mail or GMail apps, please bring advanced search from Desktop to iOS as well

Can't believe this still doesn't have the capability to specify a Folder to search in. Who doesn't have folders??

Really, it's amazing this capability wasn't put in at the very beginning as it's super obvious!

And exclude Trash by default, it's just common sense!

Ditto plus operators like has:attachment or has:pdf from:<email address> or subject:<the_subject>

If I'm standing on a folder or label, I'd like it to be selected as default search place.

Yes, I'd like to exclude Trash by default too

Would be important to enable more complex searches, like "in:labelA and not in:folderB"

I often cant find specific emails, if i cant remember the name but only keywords. Like last time I used the word bicycle a lot, but could not remember the email. I could not find it. Or contacting proton and i could not find it. I am not sure, if I do something wrong, but that really is difficult, as I have many emails runnig now on protonmail and i cant find them again :/ I would find that very urgent matter (apply to app and webbrowser)

Yes, please. And add "smart' spelling; as it is, one letter off and the search fails. It's too basic, and often fails to return any results even though the item is there when searched manually. And it's too slow. I also have the paid plan, but in may respects I miss some of the free Gmail features.

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.