[Dovecot] Disconnected: Too many invalid IMAP commands

[Gabriele]

Greetings, I'm having big issues here, hope you can help me…

Ubuntu Server 8.04, postfix 2.5.1, dovecot 1.0.10, postfixadmin (MySQL+ 
virtual users)…

I am trying to move e-mails from an old IMAP account to my new dovecot 
IMAP server accounts.
The old server is EIMS (Eudora Internet Mail Server, so a sort of mbox 
format)…
I move messages by drag 'n' dropping in Mozilla Thunderbird.

No problems with messages under 4MB size (there are huge messages, up to 
25MB), but as soon as I try to move messages from 4MB and up, the 
connection hangs, nothing happens, the application becomes barely 
responsive, I have quit and re-open it to make it behave properly.

In the logs, I read (user and IPs are fake, here):

Sep 18 07:52:06 in dovecot: imap-login: Login: user=<user at my-domain>, 
method=PLAIN, rip=123.123.123.123, lip=123.123.123.123
Sep 18 07:52:06 in dovecot: IMAP(user at my-domain): Disconnected: Too many 
invalid IMAP commands.


Could it be a client (Thunderbird) issue?
I have tried with Apple Mail 4.1, same problem, same logs.

Could it be a quota limit (googling around, I read that sometimes the 
error may be triggered by dovecot when exceeding the quota limit)
Accout usage is actually at 1%…

Could drag 'n' drop be the wrong way to have things done?
I have also downloaded the huge e-mails from EIMS to Thunderbird Local 
Folders, the problem arises when I try to upload, so the culprit seems 
to be the new "system".


I really need help at this point… any hints?

Thanks in advance for any help you will offer.

Gabriele