This is a feature Proton Mail is sorely missing. For a service with E2E encryption that sacrifices email searchability for privacy reasons (yes, I know one can enable full message search, but still!), Proton Mail should compensate by having a stellar labeling / search facility.
Instead, not only is it not stellar, it is even sub-par: what's the point of allowing for multiple labels in a message if one cannot search for messages with multiple labels? This works well only for email counts below a few dozens, when you can quickly search for emails with one label and **visually** identify the ones with another label as well.

Please, do take a look at this, it is much more important than the full-text search you implemented recently.

I group things by tag, it makes more sense then dropping them into a folder. Because it allows me to perform queries such as 'YEAR' + 'SUBJECT' + 'ACTION' using the tagging system.

Like other commenters, including similar tickets, I'm really missing Gmail's search functionality. Search operators are a must!!

Would love to see NOT <label> so I can properly delete messages that are not label with my extra special "DONOTDELETE" && "SAVE" labels :)

having ability to search multiple labels leveraging AND, OR, and NOT along with addresses, subjects, dates is kind of necessary in order to not accidentally delete labeled contents ... only decent way to purge inboxes ... and purging ones mailbox is good security hygiene

i think this functionality should be implemented with search operators so advanced users can type their search query rather than trying to use the ui. and more than just location operators should be made available. initial release should include operators for every option currently available in advanced search with the ability to invert or negate an operator. later releases should add searching by attachment type, attachment size, starred, and others that have been suggested throughout topics on uservoice.

https://protonmail.uservoice.com/forums/284483-protonmail/suggestions/42086344-search-with-multiple-labels
https://protonmail.uservoice.com/forums/284483-protonmail/suggestions/18918526-search-for-more-than-one-labelhttps://protonmail.uservoice.com/forums/284483-protonmail/suggestions/20360023-add-search-operators

Yes, yes and yes.
It doesn't make sense that the "Location" search field includes a list of choices of different nature (folder, labels).
Also add the possibility to search messages that DO NOT have a Label assigned (within a folder or not).

Unfortunately I cannot vote more, but I would really love this feature. It opens up near-limitless possibilities like GTD-Workflows etc. by combining tags.
Example for me would be: „In:bills AND NOT In:Finished“ (SQL style)

This is needed so desperately. The whole reason I opted for labels is that I can apply more than one to an email. E.g. work type (label 1) across clients (label 2), a specific thread of work for a specific client (label 1 AND label 2). Also, label 2 NOT label 1 would be useful. The purpose of labels is defeated without this.

Currently you can search for mail using only one label. For example "Project1" or "Project2" or "Issue". I want to do searches using multiple labels in the query. For example "Project1 + Issue".

This is the one feature that keeps me from going all in on ProtonMail. Like I really need this feature, filter email so fast with this feature.

similar ticket to https://protonmail.uservoice.com/forums/284483-feedback/suggestions/18918526-search-for-more-than-one-label

can we merge the votes?