==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.4.2
- Deployed with iRedMail Easy or the downloadable installer? Installer
- Linux/BSD distribution name and version:  Ubuntu 20.04
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro?   N/A
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

I went ahead and updated my iRedMail Ubuntu server from 18.04 to 20.04, thinking it would be pain free 

I followed the update guide on the iRedMail page

I followed: https://docs.iredmail.org/upgrade.dovecot.2.2-2.3.html

Following those steps things got a bit dicey, I applied the perl scripts, added the new settings into the dovecot.conf.  No matter what I do dovecot won't start, now I am in a contant battle of config settings, and errors that have me lost.   I never got to the next steps, so I have not changed the mysql backend settings.

I wound up running doveconf -Pn to generate a new config file, and I now get errors about line 45 in the file, that does not make any sense as I can not find the offending 'ssl_protocols' in the file anywhere.   I think I have most the errors ironed out, now it just mentions the phantom line 45 in the config and the ssl_dh error.  It also mentions files that don't exist with doveconf -n   see below the log output. 

Not sure what direction to head now,  just reinstall everything? Just dovecot? I am following along on the wiki page : https://wiki2.dovecot.org/Upgrading/2.3

More lost than ever at this point, so taking a break.   It all seems to center on the dovecot config file, and the mystery files it mentions.  So dovecot is totally hosed at this point.   My old config just makes matters worse, when I run the new config process it doesn't add all the settings,  I still see ssl_min_porotocol is missing, so I have to add it back each time.   So I am stuck between version 2.2 and 2.3.

Here is the last log output:

Dec 26 19:40:33 iRedMail2 dovecot: master: Dovecot v2.3.7.2 (3c910f64b) starting up for pop3, imap, sieve, lmtp (core dumps disabled)
Dec 26 19:40:33 iRedMail2 dovecot: doveconf: Warning: NOTE: You can get a new clean config file with: doveconf -Pn > dovecot-new.conf
Dec 26 19:40:33 iRedMail2 dovecot: doveconf: Warning: Obsolete setting in /etc/dovecot/dovecot.conf:45: ssl_protocols has been replaced by ssl_min_protocol
Dec 26 19:40:33 iRedMail2 dovecot: config: Warning: NOTE: You can get a new clean config file with: doveconf -Pn > dovecot-new.conf
Dec 26 19:40:33 iRedMail2 dovecot: config: Warning: Obsolete setting in /etc/dovecot/dovecot.conf:45: ssl_protocols has been replaced by ssl_min_protocol
Dec 26 19:40:33 iRedMail2 dovecot: config: Warning: please set ssl_dh=</etc/dovecot/dh.pem
Dec 26 19:40:33 iRedMail2 dovecot: config: Warning: You can generate it with: dd if=/var/lib/dovecot/ssl-parameters.dat bs=1 skip=88 | openssl dhparam -inform der > /etc/dovecot/dh.pem
Dec 26 19:41:11 iRedMail2 dovecot: stats: Error: conn stats-reader (127.0.0.1:55196): didn't reply with a valid VERSION line: EXPORT#011global
Dec 26 19:41:49 iRedMail2 dovecot: master: Dovecot v2.3.7.2 (3c910f64b) starting up for pop3, imap, sieve, lmtp (core dumps disabled)
Dec 26 19:41:49 iRedMail2 dovecot: doveconf: Warning: NOTE: You can get a new clean config file with: doveconf -Pn > dovecot-new.conf
Dec 26 19:41:49 iRedMail2 dovecot: doveconf: Warning: Obsolete setting in /etc/dovecot/dovecot.conf:45: ssl_protocols has been replaced by ssl_min_protocol
Dec 26 19:41:49 iRedMail2 dovecot: config: Warning: NOTE: You can get a new clean config file with: doveconf -Pn > dovecot-new.conf
Dec 26 19:41:49 iRedMail2 dovecot: config: Warning: Obsolete setting in /etc/dovecot/dovecot.conf:45: ssl_protocols has been replaced by ssl_min_protocol
Dec 26 19:41:49 iRedMail2 dovecot: config: Warning: please set ssl_dh=</etc/dovecot/dh.pem
Dec 26 19:41:49 iRedMail2 dovecot: config: Warning: You can generate it with: dd if=/var/lib/dovecot/ssl-parameters.dat bs=1 skip=88 | openssl dhparam -inform der > /etc/dovecot/dh.pem
Dec 26 19:41:53 iRedMail2 dovecot: stats: Error: conn stats-reader (127.0.0.1:56582): didn't reply with a valid VERSION line: EXPORT#011global
Dec 26 19:41:53 iRedMail2 dovecot: stats: Error: conn stats-reader (127.0.0.1:56584): didn't reply with a valid VERSION line: EXPORT#011global
Dec 26 19:42:14 iRedMail2 dovecot: lda: Fatal: Plugin 'stats' not found from directory /usr/lib/dovecot/modules
Dec 26 19:42:14 iRedMail2 dovecot: lda: Fatal: Plugin 'stats' not found from directory /usr/lib/dovecot/modules

Here are the mystery files mentioned with doveconf -n

root@iRedMail2:/etc/dovecot# doveconf -n | head -n 1
# 2.3.7.2 (3c910f64b): /etc/dovecot/dovecot.conf
doveconf: Error: t_readlink(/var/run/dovecot/dovecot.conf) failed: readlink() failed: No such file or directory
doveconf: Error: duplicate listener: /var/run/dovecot/stats-reader
doveconf: Fatal: Error in configuration file /etc/dovecot/dovecot.conf: duplicate listener: /var/run/dovecot/stats-reader
root@iRedMail2:/etc/dovecot#

and the most recent config file: 

# 2.3.7.2 (3c910f64b): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.7.2 ()
# OS: Linux 5.4.0-91-generic x86_64 Ubuntu 20.04.3 LTS
# Hostname: iRedMail2
auth_master_user_separator = *
auth_mechanisms = PLAIN LOGIN
deliver_log_format = from=%{from}, envelope_sender=%{from_envelope}, subject=%{subject}, msgid=%m, size=%{size}, delivery_time=%{delivery_time}ms, %$
dict {
  acl = mysql:/etc/dovecot/dovecot-share-folder.conf
  lastlogin = mysql:/etc/dovecot/dovecot-last-login.conf
  quotadict = mysql:/etc/dovecot/dovecot-used-quota.conf
}
first_valid_uid = 2000
last_valid_uid = 2000
listen = * [::]
login_log_format_elements = user=<%u> method=%m rip=%r lip=%l mpid=%e %c %k session=<%{session}>
mail_gid = 2000
mail_location = maildir:%Lh/Maildir/:INDEX=%Lh/Maildir/
mail_plugins = quota mailbox_alias acl mail_log notify old_stats
mail_uid = 2000
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 = yes
  location =
  mailbox Archive {
    auto = no
    special_use = \Archive
  }
  mailbox Archives {
    auto = no
    special_use = \Archive
  }
  mailbox "Deleted Messages" {
    auto = no
    special_use = \Trash
  }
  mailbox Drafts {
    auto = subscribe
    special_use = \Drafts
  }
  mailbox Junk {
    auto = subscribe
    special_use = \Junk
  }
  mailbox "Junk E-mail" {
    auto = no
    special_use = \Junk
  }
  mailbox Sent {
    auto = subscribe
    special_use = \Sent
  }
  mailbox "Sent Items" {
    auto = no
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    auto = no
    special_use = \Sent
  }
  mailbox Spam {
    auto = no
    special_use = \Junk
  }
  mailbox Trash {
    auto = subscribe
    special_use = \Trash
  }
  prefix =
  separator = /
  type = private
}
namespace {
  list = children
  location = maildir:%%Lh/Maildir/:INDEX=%%Lh/Maildir/Shared/%%Ld/%%Ln
  prefix = Shared/%%u/
  separator = /
  subscriptions = yes
  type = shared
}
passdb {
  args = /etc/dovecot/dovecot-mysql.conf
  driver = sql
}
passdb {
  args = /etc/dovecot/dovecot-master-users
  driver = passwd-file
  master = yes
}
plugin {
  acl = vfile
  acl_shared_dict = proxy::acl
  last_login_dict = proxy::lastlogin
  last_login_key = last-login/%s/%u/%d
  mail_log_events = delete undelete expunge copy mailbox_create mailbox_delete mailbox_rename
  mail_log_fields = uid box msgid size from subject flags
  mailbox_alias_new = Sent Messages
  mailbox_alias_new2 = Sent Items
  mailbox_alias_old = Sent
  mailbox_alias_old2 = Sent
  old_old_old_old_old_old_stats_refresh = 30 secs
  old_old_old_old_old_old_stats_track_cmds = yes
  quota = dict:user::proxy::quotadict
  quota_grace = 10%%
  quota_status_nouser = DUNNO
  quota_status_overquota = 552 5.2.2 Mailbox is full
  quota_status_success = DUNNO
  quota_warning = storage=100%% quota-warning 100 %u
  quota_warning2 = storage=95%% quota-warning 95 %u
  quota_warning3 = storage=90%% quota-warning 90 %u
  quota_warning4 = storage=85%% quota-warning 85 %u
  sieve = ~/sieve/dovecot.sieve
  sieve_before = /var/vmail/sieve/dovecot.sieve
  sieve_dir = ~/sieve
  sieve_global_dir = /var/vmail/sieve
  sieve_max_redirects = 30
  sieve_vacation_send_from_recipient = yes
}
protocols = pop3 imap sieve lmtp
service auth {
  unix_listener /var/spool/postfix/private/dovecot-auth {
    group = postfix
    mode = 0666
    user = postfix
  }
  unix_listener auth-master {
    group = vmail
    mode = 0666
    user = vmail
  }
  unix_listener auth-userdb {
    group = vmail
    mode = 0660
    user = vmail
  }
}
service dict {
  unix_listener dict {
    group = vmail
    mode = 0660
    user = vmail
  }
}
service imap-login {
  process_limit = 500
  service_count = 1
}
service lmtp {
  executable = lmtp -L
  inet_listener lmtp {
    address = 127.0.0.1
    port = 24
  }
  process_min_avail = 5
  unix_listener /var/spool/postfix/private/dovecot-lmtp {
    group = postfix
    mode = 0600
    user = postfix
  }
  user = vmail
}
service managesieve-login {
  inet_listener sieve {
    address = 127.0.0.1
    port = 4190
  }
}
service old-stats {
  fifo_listener old-stats-mail {
    group = vmail
    mode = 0644
    user = vmail
  }
  inet_listener {
    address = 127.0.0.1
    port = 24242
  }
  unix_listener stats-reader {
    group = vmail
    mode = 0660
    user = vmail
  }
  unix_listener stats-writer {
    group = vmail
    mode = 0660
    user = vmail
  }
}
service pop3-login {
  service_count = 1
}
service quota-status {
  client_limit = 1
  executable = quota-status -p postfix
  inet_listener {
    address = 127.0.0.1
    port = 12340
  }
}
service quota-warning {
  executable = script /usr/local/bin/dovecot-quota-warning.sh
  unix_listener quota-warning {
    group = vmail
    mode = 0660
    user = vmail
  }
}
ssl = required
ssl_cert = </etc/letsencrypt/live/mail.exampledomain.com/fullchain.pem
ssl_cipher_list = EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH
ssl_dh = </etc/ssl/dh2048_param.pem
ssl_key = </etc/letsencrypt/live/mail.exampledomain.com/privkey.pem
ssl_prefer_server_ciphers = yes
syslog_facility = local5
userdb {
  args = /etc/dovecot/dovecot-mysql.conf
  driver = sql
}
protocol lda {
  lda_mailbox_autocreate = yes
  lda_mailbox_autosubscribe = yes
  mail_plugins = quota mailbox_alias acl mail_log notify old_stats sieve
}
protocol lmtp {
  lmtp_save_to_detail_mailbox = yes
  mail_plugins = quota mailbox_alias acl mail_log notify old_stats sieve
  recipient_delimiter = +
}
protocol imap {
  imap_client_workarounds = tb-extra-mailbox-sep
  mail_max_userip_connections = 30
  mail_plugins = quota mailbox_alias acl mail_log notify old_stats imap_quota imap_acl imap_old_stats last_login
}
protocol pop3 {
  mail_max_userip_connections = 30
  mail_plugins = quota mailbox_alias acl mail_log notify old_stats last_login
  pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
  pop3_uidl_format = %08Xu%08Xv
}