Hallo
Before I upgraded to ubuntu lucid I used the twitter client "twidge" to get my updates send to thunderbird. I used postfix and dovecot for that.
When I tried to get the configuration to get to work again, the "test drive" worked just fine. I got the tweets in my inbox in thunderbird. Unfortunately since then, it doesn't work anymore. And I have no clue what could be the problem.
I don't get any error messages. Neither from twidge or cron. Nor from thunderbird concerning the local dovecot account. Tere's a mailbox file in /var/mail as well as in /var/spool/mail. But they stay the same size, so I guess nothing gets there.
"ps axf" showed that everything is actually running.
Guenni
So what could be the problem?

What do the postfix/dovecot/twidge logs say?

Hm, the programs obviously don't have a log file. At least none I could find.
The only thing I could find were: /var/log/mail.log

Hm, the three programs themselves don't have a log file. At least none I could find. I found: /var/log/mail.log
Hm the only useful log file I found was: /var/log/mail.log
I copied the only entry which I think is useful.
from=<guenni@guenni-laptop>, size=682, nrcpt=1 (queue active)
Jun 7 20:18:29 guenni-laptop dovecot: deliver(guenni): Fatal: Plugin cmusieve not found from directory /usr/lib/dovecot/modules/lda
Jun 7 20:18:29 guenni-laptop postfix/local[3839]: 37B7F83626: to=<guenni@guenni-laptop>, relay=local, delay=0.55, delays=0.42/0/0/0.14, dsn=4.3.0, status=deferred (temporary failure)

Unfortunately I don't know what to do about that.
aptitude search cmusieve didn't show anything. So it's not just a missing package.
Guenni

They're both logging to the /var/log/mail.log file then. CMU Seive is the local delivery agent for cyrus, which you don't appear to be using. Although that would likely explain your problem I suspect...

http://wiki.dovecot.org/LDA