After six months of Thunderbird without a single problem I gave Kontact another try. It worked fine for 4 days. I use a gmail account and included it to akonadi. The system has been set up right before and no other configuration was done. Today I tried to send an emai. The mail was moved to the outbox and nothing happend. I tried to send it multiple times by pressing "send mail" but it didn´t work. After about 90 minutes or so a message appeared which said that the „Mail Dispatcher Agent“ does´t work. I think it asked if I wanted to restart the agent (I cannot rember the correct term). I clicked yes. The mail stayed in the outbox. After some google „research“ I found out how to restart the agent using akonadiconsole. Now it works again. By the way. I´m now using Thunderbird again. Another reason for this is that Kmail takes 2 to 10 seconds to display one single email in its preview box. TB ~= 0 sec. Good work. I´ll give it a try again next year. Maybe. Reproducible: Didn't try
I also find this problem. I'm running Ubuntu Raring, akonadi 4:4.10.5-0ubuntu0.1, on x86. I find that often for long periods, I can fetch mail from gmail (via IMAP) and send mail just fine. But then, for some reason, akonadi will fail to fetch mail from gmail, and fail to send mail, too. As the OP reports, the message will sit in my outbox folder, and repeated attempts to "send queue messages" will do nothing. When this happens, it happens for two different gmail accounts I've added to akonadi. Sometimes, if I reboot my laptop and log back in, akonadi will send the message, and will start fetching mail from gmail again. Sometimes, rebooting doesn't help. Eventually, after a while, something changes, and the next reboot will fix the problem. I am unable to debug, b/c I can't find a way to get a trace of what the mail dispatcher agent is doing, that could be useful. In akonadiconsole I see nothing related to actual IMAP transport, in the tab for the "akonadi_maildispatcher_agent_NNNN". I see nothing in the akonadi_map_resource_NNN" tabs, either. If there were some instructions someplace, to clue knowledgeable technical users into how to go about debugging akonadi problems, that'd be really helpful.
It turns out, this bug was being caused by a corruption of the kde wallet. I recreated the wallet and have been working happily for a couple of weeks; then today something caused the wallet to be corrupted again, and I can no longer access my IMAP mail resources. So at least for me, this is no longer a kmail/akonadi problem.
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.