Only INBOX is searched when using gmail with dovecot FTS and solr

[hi-dovecot at mcarle.io]

Hi,

I am using https://github.com/docker-mailserver/docker-mailserver to 
setup my mailserver and added solr for full-text search. Nearly 
everything is working as expected. But I have a problem with the 
full-text search, as I have a lot of folders in my mailbox and I just 
can't find any mail in any of these folders except INBOX when I search 
with the Gmail android app.

After analyzing the logs, I assume, that the bug is in the Gmail app, as 
it is only searching in the INBOX folder. I searched a bit and found 
some reports of other users confirming that. As this "design decision" 
(or bug) is quite old, I assume that Google won't fix it. But as many 
people are using Gmail, I assume that there must be a way to search all 
folders with Gmail. Sadly, I haven't found any possibility yet.

As a workaround one may put a proxy in between and simply remove the 
"+box:123" filter from the path (e.g. with a small regex). With that, 
solr will return all found mails from that user, regardless of the 
folder. This may be a quite simple, but very dirty hack.

Hence, I hope that you guys know a better way, a good way to overcome 
this issue and enable all Gmail users to search for email in all folders.

Best regards,

Marcel