Additional information that every flags lost in the mail list not only "attached".

For example:
If I reply or forward a mail the kmail shows this with a little arrow in the message list. Few mins later there are gone, I see only "normal" icon before subject. Sometime it's not so good. Pls fix this issue, please!!!!

I can confirm this bug in Kubuntu 11.10 using KDE 4.7.3. Attachments are shown sometimes in the message list, but disappear. Same for other info like the forwarded email icon. The "important" icon does not disappear.

It seems to be very random behaviour, the icons disappear 90% of the time instantly when receiving the mail or at actions like hovering over the message list or clicking on the message. Sometimes the icons are shown for a few minutes and disappear after a while without doing anything.

I'm using an IMAP account and have several filters in use which are instantly applied when mail arrives, so I guess the filters may not be the problem. It wasn't a fresh install, I did an upgrade from Kubuntu 11.04 a while ago and used the Kmail migration assistant (for which I should write a dozen other bug reports...)

Confirmed in 4.7.4.  Also, setting the quick-search "status" dropdown to "attachments" doesn't show any mails - seems like it could be related.

Can confirm this on Kubuntu 12.04 with kde sc 4.8.4. I fiddeled around with some circumstances.
The mails have icons immediately after they are fetched from the server. But after the next impa-sync, the are deleted. No difference with any config option in the imap-settings. The problem does not occur when i fetch my mails from the same server with pop3. It does also not occur more seldom on another server. The most problematic server is a company imap-server which runs on exchange. The missing reply-icons are always missing on imap with exchange and never on imap with the unix-server. The attachment icons are always missing on the imap-exchange, but also sometimes on unix server.

Yep I confirm that for me (see comment #3) the lack of icons is on an Exchange DIMAP server.   Having read #4 I also setup a local DIMAP server on my Linux mailbox as a test, and that *does* get icons.

Unfortunately I can't wire-trace the Exchange IMAP conversation as it uses SSL.  Can I get a trace out of Akonadi or something ?

This is still a problem with Exchange IMAP accounts in KDE 4.9

Thank you for your feedback. Setting status to confirmed, bump version.

can confirm on 4.9 backports on ubuntu 12.04. It works with pop over the same email account.

Bug confirmed in gentoo with:

mike@münchen ~ $ kmail --version
Qt: 4.8.2
KDE Development Platform: 4.9.3
KMail: 4.9.3

Here some info about the IMAP server (MS Exchange Server 2003 ver. 6.5.7638.1):

mike@münchen ~ $ telnet our.imap.server.address 143
Trying our.imap.server.address...
Connected to our.imap.server.address.
Escape character is '^]'.
* OK Server IMAP4rev1 di Microsoft Exchange Server 2003 versione 6.5.7638.1 (MAILCHANGE.obscured.imap.domain.address) pronto.
a001 capability
* CAPABILITY IMAP4 IMAP4rev1 IDLE LOGIN-REFERRALS MAILBOX-REFERRALS NAMESPACE LITERAL+ UIDPLUS CHILDREN AUTH=NTLM
a001 OK CAPABILITY completed.
a002 logout
* BYE Disconnessione del server IMAP4rev1 di Microsoft Exchange Server 2003 versione 6.5.7638.1 in corso...
a002 OK LOGOUT completed.
Connection closed by foreign host.

Still an issue in 4.11.1.

It seems that Kmail and/or Akonadi is trying to do something but DIMAP Exchange is replying with an error, as I am now getting the following notification when I do anything that involves a property change 

"<Resource>: Store failed, server replied A001710 BAD Command Argument Error: 11"

The A-number varies, I've seen A001710, A001871 and A000005, presumably that is IMAP ID-related.

Happens for me as well, talking to a local Dovecot server on Gentoo (amd64 stable).  Please let me know if there's info I can provide to help.

$ telnet localhost 143
Trying ::1...
Connected to localhost.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=PLAIN] Dovecot ready.
a001 CAPABILITY
* CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=PLAIN
a001 OK Pre-login capabilities listed, post-login capabilities have more.
a002 LOGOUT
* BYE Logging out
a002 OK Logout completed.
Connection closed by foreign host.
$ kmail --version
Qt: 4.8.5
KDE Development Platform: 4.12.5
KMail: 4.12.5
$ eix -ce dovecot
[I] net-mail/dovecot (2.2.13-r1{tbz2}@05/31/2014): An IMAP and POP3 server written with security primarily in mind

bug 291332 sugests that attachment icon issue is in Akonadi and not Kmail. I've filed bug https://bugs.kde.org/show_bug.cgi?id=342756 for Akonadi, but it has no response yet.

Git commit 0cb0e2f5efc7d76033f9b9ccc83aeebe9845f338 by Martin Koller.
Committed on 31/01/2015 at 14:44.
Pushed by mkoller into branch 'KDE/4.14'.

Fix missing mail flags; avoid code duplication

This patch uses the new method Akonadi::MessageFlags::copyMessageFlags()
to copy the mail message flags into Akonadi objects, avoiding
code duplication.
Some places did not do this previously leading to mail flags never
appearing (or getting lost) in Akonadi
Related: bug 313401, bug 327241, bug 342756
FIXED-IN: 4.14.6
REVIEW: 122224

M  +1    -1    CMakeLists.txt
M  +1    -13   resources/imap/messagehelper.cpp
M  +3    -0    resources/maildir/maildirresource.cpp
M  +2    -0    resources/maildir/retrieveitemsjob.cpp
M  +6    -0    resources/mbox/mboxresource.cpp
M  +3    -0    resources/mixedmaildir/mixedmaildirstore.cpp
M  +2    -9    resources/pop3/pop3resource.cpp

http://commits.kde.org/kdepim-runtime/0cb0e2f5efc7d76033f9b9ccc83aeebe9845f338

Doenst work for me on KMail 4.14.6

Testen in Gentoo and Archlinux

Doenst work for me on KMail 4.14.6

Tested in Gentoo and Archlinux

Doenst work for me on KMail 4.14.6

Tested in Gentoo and Archlinux

Sorry for the triple post, something went wrong with the browser.

Do you want/need any screenshot or othre type of proof?

The Icon is there, but after some time of amount, it just disappears (it doesnt last longer than 1 minute)

I hate to be the party pooper. But I also still have problems with the attachment icon showing up only randomly in the message list. This whole feature actually *never* worked reliable for me in the whole KMail 4.x + 5.x series.

Running kmail 5.2.3. Anything where I can help debugging?

Still valid for 5.4.1, although it's quite hard to tell. The icons are so tiny, pixelated and similar that you hardly get their meaning.

This is still an open bug :(
More info: attachment icon disappear when in message list i use "smart with clickable status" theme.

This does not apply when using "smart" or "classic" message list theme.

Steps:
receive email with attachment
click read/unread icon status (with smart with clickcable status theme)
icon attachment disappear

ubuntu neon
kmail 5.18.1
kde plasma 5.22.5
kde framework 2.86.0
qt version 5.15.3
kernel version 5.11.0-34-generic
graphic platform x11