My left and right arrows are configured as shortcuts to navigate to the previous and to the next message in KMail's message list. However, they are also collapsing and expanding threads, despite they are not the configured shortcut for these actions (I use "-" and "+" for that). This makes it impossible to navigate through the message list using the keyboard if messages are shown in threads. When I try to go to the previous message, KMail collapses the thread instead. Then, if I try to go to the next message, it expands the thread. If I type the left key several times, it collapses the thread and then go to the previous messages. Also, the left and right keys often stop navigating through the messages (maybe KMail is trying to collapse/expand even if there are no other messages in the thread?). When this happens, I have to click another message using the mouse and then the arrows start working for navigation again. Sometimes, if I type the left and right keys several times in a row, they start navigating again without having to click other message with the mouse.
I confirm. Using 4.8.4 here. I have observed this when the message list is setup with the classic theme with aggregation. The keyboard shortcut keys LEFT (prev msg) and RIGHT (next msg) sometimes work as expected, and sometimes expand/collapse the aggregated messages. I also have seen cases where keys LEFT and RIGHT expand/collapse threaded emails instead of going to the previous/next email. Keys P and N are also mapped to the prev/next msg actions, but do not always work for reasons hard to decipher. I suspect that this happens when the aggregation headers get the input focus for some reason. Maybe calling setFocusPolicy(Qt::NoFocus) on the aggregation headers would eliminate this.
I can confirm this behaviour. My setup is : KDE 4.9 openSuSE 12.2 with kmail "view" - > "message list" -> "sorting" -> "by date/time" and "most recent on top" also "message list" -> "aggregation" -> "standard mailing list" and "message list" -> "theme" -> "classic" and "headers" -> "fancy headers"
This bug has only been reported for versions before 4.14, which have been unsupported for at least two years now. Can anyone tell if this bug still present? If noone confirms this bug for a Framework-based version of kmail2 (version 5.0 or later, as part of KDE Applications 15.12 or later), it gets closed in about three months.
Just as announced in my last comment, I close this bug. If you encounter it again in a recent version (at least 5.0 aka 15.08), please open a new one unless it already exists. Thank you for all your input.