My personal KDEPIM upgrade (again): laptop

One year after my last blog post on this topic I encountered some minor difficulties with combining KDEPIM-4.4 (i.e. kmail1) and the KDE 4.10 betas. These difficulties are fixed now, and the combination seems to work fine again. Anyway, I became curious about the level of stability of Akonadi-based kmail2 once more. After all, I've been running it continuously over the year on my office desktop with a constant-on fast internet connection, and that works quite well. So, I gave it a fresh try on my laptop too. I deleted my Akonadi configuration and cache, switched to Akonadi mysql backend, updated kmail and the rest of KDEPIM without migrating to 4.9.4, and re-added my IMAP account from scratch (with "Enable offline mode"). The overall use case description is "laptop with large amount of cached files from IMAP account, fluctuating internet connectivity". Now, here are my impressions...

• Reaction time is occasionally sluggish, but overall OK.
• The progress indicator behaves a bit odd, it checks the mail folders in seemingly random order and only knows 0% and 100% completion.
• Random warning messages. It seems that kmail2 uses some features that "my" IMAP server does not understand. So, I'm getting frequent warning notifications that don't tell me anything and that I cannot do anything about. SET ANNOTATION, UID, ... Please either handle the errors, inform the user what exactly goes wrong, or ignore them in case they are irrelevant. Filed as a wish, bug 311265.
• Network activity stops working sometime. This sounds worse than it actually is, since in 99% of all cases Akonadi now detects fine that the connection to the server is broken (e.g., after suspend/resume, after switching to a different WLAN, or after enabling a VPN tunnel) and reconnects immediately. In the few remaining cases, re-starting the Akonadi server does the trick. You just have to know what to kick.
• More problematic is, while you're in online mode, any problems with connectivity will make kmail "hang". Clicking on a message leads to an attempt to retrieve it, which requires some response from the network. As it seems to me, all such requests are queued up for Akonadi to handle, and if that does not get a reply, pending requests are stuck in the queue... OK, you might say that this is a typical use case for offline mode, but then I would have to be able to predict when exactly my train enters the tunnel... Compare this to kmail1 disconnected IMAP accounts, where regular syncing would be delayed, but local work remained unaffected.
• Offline mode is a nice concept, and half a solution for the last problem, but unfortunately it does not work as expected. For mysterious reasons, a considerable part of the messages is not cached locally. I switch my account to offline mode, click on a message, and obtain an error message "Cannot fetch this in offline mode". Well, bummer. Bug 285935.
• This may just be my personal taste, but once something goes wrong (e.g., non-kde related crash, battery empty, ...) and the cache becomes corrupted somehow, I'd like to be able to do something from kmail2 without having to fiddle with akonadiconsole. A nice addition would be "Invalidate cache" in the context menu of a mail folder, or some sort of maintenance menu with semi-safe options.
• Finally... something is definitely going wrong with PGP signatures; the signatures do not always verify on other mail clients. Tracking this down, it seems that CRLF is not preserved in messages, see bug 306005.

On the whole, for the laptop use case the "new" KDEPIM is now (4.9.4) more mature than the last time I tried. I'll keep it now and not downgrade again, but there are still some significant rough edges. The good thing is, the KDEPIM developers are aware of the above issues and debugging is going on, as you can see for example from this blog post by Alex Fiestas (whose use case pretty much mirrors my own).