dovecot - Jun 2017 - Error: vsize-hdr has invalid size

version
  2.2.27 (c0f36b0)


For one user logs have a lot of  these since recent upgrade from debian
jessie to stretch :
Jun 28 13:08:18 imap dovecot: imap(tfa): Error: vsize-hdr has invalid size:
36


Only one user has the issue.  It has been happening for a month,  The user
reports no issue on his end reading mail.

Is there a way to fix the error ?


best regards, Roberto


# dovecot -n
# 2.2.27 (c0f36b0): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.4.16 (fed8554)
# OS: Linux 4.9.0-3-amd64 x86_64 Debian 9.0
auth_mechanisms = plain login
auth_username_format = %Ln
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
mail_location = maildir:~/Maildir
mail_plugins = " quota"
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character
vacation subaddress comparator-i;ascii-numeric relational regex imap4flags
copy include variables body enotify environment mailbox date index ihave
duplicate mime foreverypart extracttext
namespace inbox {
  inbox = yes
  location   mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix = INBOX.
  separator = .
  type = private
}
passdb {
  args = /etc/dovecot/dovecot-ldaps.conf.ext
  driver = ldap
}
plugin {
  mail_plugins = quota sieve
  sieve = ~/.dovecot.sieve
  sieve_before = /etc/dovecot/sieve/spam.sieve
  sieve_dir = ~/sieve
  sieve_global_dir = /etc/dovecot/sieve/
}
postmaster_address = .
protocols = " imap lmtp sieve"
quota_full_tempfail = yes
service auth-worker {
  user = $default_internal_user
}
service auth {
  unix_listener /var/spool/postfix/private/auth {
    mode = 0666
  }
  unix_listener auth-userdb {
    group = postfix
    mode = 0600
    user = postfix
  }
}
service imap-login {
  service_count = 0
  vsz_limit = 128 M
}
service imap {
  process_limit = 2048
}
service lmtp {
  inet_listener lmtp {
    address = x.x.x.x 127.0.0.1 ::1
    port = 24
  }
}
service managesieve-login {
  inet_listener sieve {
    port = 4190
  }
  process_min_avail = 1
  service_count = 0
  vsz_limit = 256 M
}
ssl = required
ssl_ca = ..hidden
ssl_cert = ..hiden
ssl_key =  # hidden, use -P to show it
userdb {
  args = /etc/dovecot/dovecot-ldaps.conf.ext
  driver = ldap
}
protocol lmtp {
  mail_plugins = quota sieve
}
protocol imap {
  mail_max_userip_connections = 50
  mail_plugins = " quota imap_quota antispam"
  plugin {
    antispam_backend = pipe
    antispam_pipe_program = /fbc/bin/mail/sa-learn-pipe.sh
    antispam_pipe_program_notspam_arg = --ham
    antispam_pipe_program_spam_arg = --spam
    antispam_spam = Junk
    antispam_trash = Trash
  }
}
protocol sieve {
  mail_debug = yes