> Hi, Sergei.  I'm not clear on where exactly you are seeing a problem
> with this tab in the subject line.  Is it showing up somewhere you think
> it shouldn't?

It is shown in e.g. `notmuch show` as well as
'notmuch_message_get_header(m, "subject")`

> I'm not sure libnotmuch should be doing any scrubbing of the message
> contents.  The emacs UI does seem to replace the tab with a space,
> though.  Maybe other MUAs should be doing the same?

My point is that this tabulation character does not relate to the
contents of the header (this might be arguable though) and libnotmuch
should return the contents, not its representation on file system.

-- 
С уважением,
Сергей Шиловский
Sergei Shilovsky