Yes it does.

Sounds like Duplicate of #13430

@peo: Can you confirm this fixes?

ok so, i upgraded package Horde_Imap_Client  from 2.24.1 to 2.24.2 and 
it's working now

And FWIW, I directly checked out imp-6.2.1 tag and everything works fine.

Logged onto IMP, I enter this command directly into a separate IMAP session:

a uid store 66460 -flags \seen
* 11 FETCH (UID 66460 FLAGS ())
a OK Store completed.

and the message goes from seen -> unseen in IMP.  Issuing this command:

a uid store 66460 +flags \Flagged
* 11 FETCH (UID 66460 FLAGS (\Flagged))
a OK Store completed.

correctly updates the flag also.

Outgoing AJAX request:

poll        ["SU5CT1g"]
token        LuLsFrvM6Rv4mVhLiMHxCA1
view        SU5CT1g
viewport        {"view":"SU5CT1g","cacheid":"VTY2NDYyLFYxMjU1Njg1MzM3LEgxMjQ4OTc=|9|0|D230","slice":"1:182","cache":"58302,65445,65458,65608,65678,65904,66062,66317,66434,66459:66460"}

Response:

/*-secure-{"response":true,"tasks":{"imp:viewport":{"label":"Inbox","totalrows":11,"rowlist_reset":true,"rowlist":{"58302":1,"65445":2,"65458":3,"65608":4,"65678":5,"65904":6,"66062":7,"66317":8,"66434":9,"66459":10,"66460":11},"data":{"66460":[msg data 
redacted]},"cacheid":"VTY2NDYyLFYxMjU1Njg1MzM3LEgxMjQ4OTg=|9|0|D230","view":"SU5CT1g","metadata":{"thread":{"58302":"","65445":"3","65458":"4","65608":"","65678":"","65904":"","66062":"","66317":"","66434":"","66459":"4","66460":"04"}}},"imp:poll":{"SU5CT1g":1}}}*/

I am testing on the stable branch FRAMEWORK_5_2.  (Which is ~IMP 
6.2.2).  We don't test with the actual code of a release version 
because that is irrelevant, since the bug may have already been fixed. 
  (This is the responsibility of a bug reporter to verify, not a 
developer.)

I don't recall anything in IMP recently fixed that would cause this 
issue.  More important, I use multiple MUAs to read my mail and I have 
never experienced mis-syncing of emails, at least in the last 6 months 
or so.

A good place to begin debugging is the poll() function in 
IMP_Ajax_Application_Handler_Common.  Immediately after a remote 
change in the mailbox and a poll() request is issued, the 
$this->_base->changed() call will return a non-empty value.  if that 
call is returning false then something is different on your system 
than mine.

Steps how to reproduce:
1.) Login with IMP to e-mail account.
2.) Login with Thunderbird to the same e-mail account as in (1).
3.) Mark any message in inbox with Thunderbird as unread.
4.) Look into IMP, click on Refresh button and see that message
is still marked as seen in message list (it is not bolded).
5.) Also notice, that favicon and folder tree is correctly updated
(they will show one unseen message) - YES, this was correctly updated 
also now using Thunderbird (so message is really marked as unseen on 
the server).

Always reproducable, Dovecot 2.2.9, IMP 6.2.1, Thunderbird 31.0 (all 
linux). The only way how to
correctly update the message list in IMP is CTRL-F5 or relogin (this 
is another proof that message was really marked as unseen on the 
server).

Michael, are you REALLE REALLY testing this on *STABLE* versions? I 
still very well remember the case where i spend hours of debuging and 
proofing while you were simply running already fixed git version (and 
you didn't tell anybody). Please note that affected version is set to 
6.2.1 and, in my case, i have every other package on newest STABLE 
version.

In other words:

1. Log into IMP
2. Log into another non-IMP MUA
3. Make change in non-IMP MUA (ensure that this change is actually 
propogated to the server. Some MUA's may not immediately send changes 
to the IMAP server).
4. Refresh IMP mailbox

In this scenario, I always see the updates in IMP.

The original post said the changes to the mail account were done via 
an *external* (non-IMP) mail agent.  That is what I am testing.

I am not going to test changes done via a separate IMP window until I 
verify that this cannot be reproduced by others because that is 
potentially a separate issue than what was originally reported.

Steps how to reproduce:
1.) Login in browser1 to e-mail account.
2.) Login in browser2 to the same e-mail account as in (1).
3.) Mark any message in inbox via browser1 as unseen.
4.) Look into browser2, click on Refresh button and see that message 
is still marked as seen in message list (it is not bolded).
5.) Also notice, that favicon and folder tree is correctly updated 
(they will show one unseen message).

Always reproducable, Dovecot 2.2.9, IMP 6.2.1. The only way how to 
correctly update the message list is CTRL-F5 or relogin.

Yes, IMP does that, but is only reflected in the browser tab and 
"Inbox" item in left column, not in the actual mail list.

This happens in our setup and apparently for one more user as reported 
on the list. So, if it is not a bug, where should one look if the 
problem is in our end?

Verified working in FRAMEWORK_5_2 and master.

In mailbox, changed a flag on a message currently loaded into IMP via 
a separate client.  On next poll, message flag was correctly updated 
in IMP.

Outgoing poll request had this cacheid:

"VTY2MzYwLFYxMjU1Njg1MzM3LEgxMjQ2NDQ=|9|0|D228"

Response had this cacheid:

"VTY2MzYwLFYxMjU1Njg1MzM3LEgxMjQ2NDU=|9|0|D228"

So cacheid (which is what controls update trigger) changed, indicating 
that IMP correctly determined that the mailbox had changed.

Horde 5.2.1 / imp 6.2.1
When set to update at regular intervals, changes to read/unread done in
another mail reader / IMP window are only visible in the browser tab 
and "Inbox" in
the left column.
The mail list is NOT updated, not even if ones clicks the "Refresh"
button, browser tab and "Inbox" IS updated.
This is a change from 5.1.6/6.1.7 that we currently run in production
where all three places are properly updated.

This would be a problem if more than one user uses the same email 
account as changes are not clearly visible.