dovecot: imap Error: read : Broken pipe

[Carl St-Laurent]

Hi everyone,

I'm trying to find a solution for this bug who appears 2 months ago :

dovecot: imap(%USER%): Error: read(<binary stream of mailbox INBOX UID 
(%d)>) failed: Broken pipe (FETCH BINARY[2] for mailbox INBOX UID (%d)

Where %USER% is the unix user and %d the UID of the mailbox.

This error appears each time a user tries to download an attachment from 
one of his emails. Whether with RoundCube or Thunderbird via VPN or not. 
I thought that it was related to my firewall but no. Furthermore the 
problem isn't present when users are at the office. Upload speed from 
our ADSL connection is pretty slow about 1mpbs, I thought maybe it was 
related but it was working fine since 2 years. So I'm really short of 
ideas.

Anyone could help me please ?

Best regards,
Carl


# 2.2.27 (c0f36b0): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.4.16 (fed8554)
# OS: Linux 4.9.0-7-amd64 x86_64 Debian 9.5
auth_mechanisms = plain login
disable_plaintext_auth = no
mail_location = maildir:~/Maildir
namespace inbox {
   inbox = yes
   location =
   mailbox Drafts {
     auto = subscribe
     special_use = \Drafts
   }
   mailbox Junk {
     auto = subscribe
     special_use = \Junk
   }
   mailbox Sent {
     auto = subscribe
     special_use = \Sent
   }
   mailbox "Sent Messages" {
     special_use = \Sent
   }
   mailbox Trash {
     auto = subscribe
     special_use = \Trash
   }
   prefix =
}
passdb {
   driver = pam
}
plugin {
   sieve = file:~/sieve;active=~/.dovecot.sieve
   sieve_after = /etc/dovecot/sieve-after
}
protocols = imap imap
service auth {
   unix_listener /var/spool/postfix/private/auth {
     group = postfix
     mode = 0660
     user = postfix
   }
}
service imap-login {
   inet_listener imap {
     port = 0
   }
   inet_listener imaps {
     port = 993
     ssl = yes
   }
}
ssl = required
ssl_ca = </etc/ssl/mail/****.pem
ssl_cert = </etc/ssl/mail/****.pem
ssl_key =  # hidden, use -P to show it
userdb {
   driver = passwd
}
protocol lmtp {
   mail_plugins = sieve
}
protocol lda {
   mail_plugins = sieve
}