Changes have been made in Git for this ticket:

Bug #10480: Match Outlook vertical style a bit more

  1 files changed, 1 insertions(+), 0 deletions(-)
http://git.horde.org/horde-git/-/commit/21be4f4a74e1fe74349a75302c512754faa676af

Made one further change to match the Outlook style a bit more.   
Namely, made the subject text a lighter color than the first row text 
(see, e.g.: 
http://support.postbox-inc.com/attachments/token/ik1s16duyre1qwo/?name=B000HCXKLC-2-lg.jpg)

Same here, I don't use it, I don't like it, and I don't care. :)

I am almost convinced that the way I had implemented it before was 
based on a mockup of Outlook (or some other MUA).  I personally don't 
like it, but I like it more than the recent changes (w/everything in 
the same font face/style).  IIRC, the idea of the vertical view is to 
make the SENDER of the message stand out, vs. a horizontal view where 
the SUBJECT is more important.

So, FWIW, I would rather see this change reverted.  But since I am not 
a big vertical user, maybe someone who does use it more often (e.g. 
Chuck) can chime in.

I think a thread/conversation view would help here. One entry per 
thread/conversation on the left, however many messages there are in 
the conversation on the right. I'd love to see this.

It really must be personal taste.

Then again, threaded view is by far the most important mailbox 
visualization for me.  (IMHO we have the best threaded mailbox view 
available.)  And threaded view is pretty much worthless in the 
vertical layout, so that could be my hang-up.

fwiw, this is the view I use and I love it and wouldn't switch back. 
If you're looking for better models for it than outlook, try iOS mail 
on a tablet, gmail on a tablet, the new offline gmail, and possibly 
Mobile Me mail...

Join the club.  I find the horizontal mode extremely difficult to 
visualize also.  I tried to replicate Outlook, because that was the 
spec given to me at the time of implementation.  At the time, I 
mentioned that I personally believed the view was crap, but I was told 
that "users like this view".  Sort of wishing that I didn't add this 
view now, since it is an example of adding something simply because 
users are lemmings (this is the way X works, so...) vs. the view 
actually bringing anything positive with respect to UI/usability.

http://git.horde.org/horde-git/-/commit/671d2c3ce25bb5a5c287ee57f27d5273c72ad1f5

This seems to be done intentionally. I tried how it looked like when 
not enforcing bold to the sender/date line and italic to the subject 
line. The list indeed looks more like the list in horizontal mode 
then, but the problem is, that it's much harder for the eyed to 
distinct the rows of different messages, because in vertical mode 
those are two-line rows. I tried adding horizontal borders, but I'm 
not happy with that either.

Good morning,

     Messages marked as read are still in bold in subject in vertical 
mode. This does not occur in horizontal mode.

Thanks.