[Dovecot] very frequent disconnections

[Dan Christensen]

I've installed dovecot 1:1.1.11-0ubuntu4.1 on my jaunty system.
Access from the same host works well, but when I access remotely
(from various MUAs and networks) I get *very* frequent disconnects.
Authentication is fine, and I can usually open a mail folder,
but larger operations such as copying 20 messages into an imap
folder always get disconnected.

I can reconnect, but I often get disconnected again in a few seconds,
especially if I do more than very light access.

I've enabled all the logging I'm aware of, but I don't see any
explanations.  I get things like

Oct  7 20:19:38 jdc dovecot: auth(default): new auth connection: pid=390
Oct  7 20:19:39 jdc dovecot: auth(default): client in: AUTH^I1^IPLAIN^Iservice=imap^Isecured^Ilip=129.100.75.85^Irip=65.95.132.250^Ilport=143^Irport=62044^Iresp=<hidden>
Oct  7 20:19:39 jdc dovecot: auth-worker(default): pam(jdc,65.95.132.250): lookup service=dovecot
Oct  7 20:19:39 jdc dovecot: auth-worker(default): pam(jdc,65.95.132.250): #1/1 style=1 msg=Password: 
Oct  7 20:19:39 jdc dovecot: auth(default): client out: OK^I1^Iuser=jdc
Oct  7 20:19:39 jdc dovecot: auth(default): master in: REQUEST^I2^I367^I1
Oct  7 20:19:39 jdc dovecot: auth(default): passwd(jdc,65.95.132.250): lookup
Oct  7 20:19:39 jdc dovecot: auth(default): master out: USER^I2^Ijdc^Isystem_user=jdc^Iuid=1000^Igid=1000^Ihome=/home/jdc
Oct  7 20:19:39 jdc dovecot: IMAP(jdc): Effective uid=1000, gid=1000, home=/home/jdc
Oct  7 20:19:39 jdc dovecot: IMAP(jdc): maildir: data=~/Maildir
Oct  7 20:19:39 jdc dovecot: IMAP(jdc): maildir++: root=/home/jdc/Maildir, index=, control=, inbox=/home/jdc/Maildir
Oct  7 20:19:40 jdc dovecot: IMAP(jdc): Connection closed bytes=303/1423

and

Oct  7 20:43:54 jdc dovecot: auth(default): new auth connection: pid=6620
Oct  7 20:43:55 jdc dovecot: auth(default): client in: AUTH^I1^IPLAIN^Iservice=imap^Isecured^Ilip=129.100.75.85^Irip=65.95.132.250^Ilport=143^Irport=62633^Iresp=<hidden>
Oct  7 20:43:55 jdc dovecot: auth-worker(default): pam(jdc,65.95.132.250): lookup service=dovecot
Oct  7 20:43:55 jdc dovecot: auth-worker(default): pam(jdc,65.95.132.250): #1/1 style=1 msg=Password: 
Oct  7 20:43:55 jdc dovecot: auth(default): client out: OK^I1^Iuser=jdc
Oct  7 20:43:55 jdc dovecot: auth(default): master in: REQUEST^I5^I6594^I1
Oct  7 20:43:55 jdc dovecot: auth(default): passwd(jdc,65.95.132.250): lookup
Oct  7 20:43:55 jdc dovecot: auth(default): master out: USER^I5^Ijdc^Isystem_user=jdc^Iuid=1000^Igid=1000^Ihome=/home/jdc
Oct  7 20:43:55 jdc dovecot: imap-login: Login: user=<jdc>, method=PLAIN, rip=65.95.132.250, lip=129.100.75.85, TLS
Oct  7 20:43:55 jdc dovecot: IMAP(jdc): Effective uid=1000, gid=1000, home=/home/jdc
Oct  7 20:43:55 jdc dovecot: IMAP(jdc): maildir: data=~/Maildir
Oct  7 20:43:55 jdc dovecot: IMAP(jdc): maildir++: root=/home/jdc/Maildir, index=, control=, inbox=/home/jdc/Maildir
Oct  7 20:44:00 jdc dovecot: IMAP(jdc): Disconnected in APPEND bytes=1081/1965

The output of dovecot -n is:

# 1.1.11: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.28-15-generic x86_64 Ubuntu 9.04 
log_timestamp: %Y-%m-%d %H:%M:%S 
ssl_cert_file: /etc/ssl/certs/dovecot.pem
ssl_key_file: /etc/ssl/private/dovecot.pem
verbose_ssl: yes
login_dir: /var/run/dovecot/login
login_executable: /usr/lib/dovecot/imap-login
login_greeting_capability: yes
max_mail_processes: 25
mail_max_userip_connections: 20
mail_privileged_group: mail
mail_location: maildir:~/Maildir
mail_debug: yes
maildir_copy_preserve_filename: yes
auth default:
  verbose: yes
  debug: yes
  passdb:
    driver: pam
  userdb:
    driver: passwd

The clients I have tried are Gnus (with starttls and gnutls-cli) and
evolution, on a jaunty system;  and k9mail-beta on an HTC Dream cell
phone.  All four configurations show similar connection issues, and
the jaunty client system has a solid DSL connection to the server.
The clients don't have informative error messages either.  To them it
just appears that the connection was closed.

Any idea what could be causing this?  Or how to debug it?

Thanks,

Dan

-- 
Dan Christensen
jdc at uwo.ca