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From: David Bremner <david@tethera.net>
To: Brian May <brian@linuxpenguins.xyz>, notmuch@notmuchmail.org
Subject: Re: searching for multiple tags
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References: <87muz7nv2h.fsf@silverfish.pri>
Date: Sat, 17 Mar 2018 08:08:33 -0300
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Brian May <brian@linuxpenguins.xyz> writes:

> Hello,
>
> How do I search for emails containing multiple tags?
>
> I have tried:
>
> tag:unread tag:important
>
> However, this finds emails that contain either the unread tag or the
> important tag. Not emails that contain both.
>
> Am I doing something wrong?

This is a design-choice/quirk of the Xapian query parser, discussed
under "Operators" in man notmuch-search-terms; terms with a common
prefix are implicitely combined with an OR.
I don't think that documentation has changed since 0.23, but you can
compare with https://notmuchmail.org/manpages/notmuch-search-terms-7/

d