kmail version : 4.8.5 in account / receive / modify / advanced tab, 'enable imap idle' is translated to '启用离线模式', i think this is a bad translation. when imap idle is working, there must be a long connection established between the client and server. this is not called "离线模式". i spent several hours to explore why imap idle is not working in kmail because of this translation. i think "启用IMAP IDLE特性" or even "启用IMAP邮件推送" is better. most of normal users don't know and dont care the differnce between imap idle and push mail.
The coressponding English string is "Enable disconnected mode", AFAIK this is the option to download all message and store it locally. I grep all the translation template, and there is no "enable imap idle" string. Please switch locale to English to make sure your translation bug report is valid. (Systems settings -> Locale -> American English)
according to my test, this option at least functions just like 'enable imap idle'. maybe the author 's native language is not english, and "Enable disconnected mode" is just a translation ？ switching locale is not needed, i think a snapshot is enough .
Created attachment 75798 [details] the option underlined is what i meant.
I'm definitely sure about "Enable disconnected mode" is the original string. And some corresponding string is "Defines if all the IMAP data should be cached locally all the time" (Describe the "DisconnectedMode"). AFAIK from translation string, there is no option about IMAP IDLE, and though I'm not an expert of kdepim, but I did look into the code, there is no option to disable the "IDLE" feature, "IDLE" will be always enabled. And disconnected mode only means it will also fetch the "body" on updates. I think you misunderstand the option. There is three possible reason: 1. your imap server doesn't support idle, which can be checked from server side capacities (check it by last button in your screenshot). 2. your imap server have some bug in supporting idle. 3. idle mode have bug in kmail. But it's definitely not a translation bug. I'll close this report, and feel free to open a new bug report about idle mode against kresources -> imap, and remember to include the imap server you're using to help developer do the debug.