Connection closed reason

[Miloslav Hůla]

Hi,

we have one user using the old Alpine client with IMAP. Time to time (3 
times per day or 3 times per week) he get error: "MAIL FOLDER INBOX 
CLOSED DUE TO ACCESS ERROR" and he complains, that inbox stops to 
refresh with new emails.

I don't know Alpine but I can imagine, that Alpine creates TCP 
connection to IMAPS and uses IDLE. I read wiki page about Timeouts [1] 
and it seems OK. Alpine is connected 5 or more hours without interrupt. 
But I found 'Connection closed' at approximate times of user reports in 
mail.log.

Am'I undestand it correctly, that 'Connection closed' is some kind of 
incorrect connection end? I can find 'Logged out' messages which seems 
to me as correct ones.

I can imagine that such situations may happend for moving clients, such 
a smartphone with losing signal. But mentioned user is on local network 
connected by cable.

I'm interested, what exactly 'Connection closed' in mail log means. We 
have following lines in log:


dovecot: imap(username): Connection closed in=63 out=288442

dovecot: imap(username): Connection closed (IDLE running for 0.001 + 
waiting input for 0.001 secs, 2 B in + 10+0 B out, state=wait-input) 
in=9668 out=17375

imap(username): Connection closed: read(size=3751) failed: Connection 
reset by peer in=4441 out=51431

dovecot: imap(username): Connection closed (UID fetch running for 0.008 
+ waiting input for 0.001 secs, 0.001 in locks, 101 B in + 202+202 B 
out, state=wait-input) in=3330 out=436043


Could it be problem in our network or Dovecot configuration issue? Can I 
somehow debug all connections for single client?

Thank you, Milo


[1] https://wiki.dovecot.org/Timeouts