Hallo Zusammen,
nach stundenlangem selber Suche hoffe ich hier Hilfe zu bekommen.
Heute habe ich ein Unbuntu 20.04 Update gefahren und sofort danach war das Haupt-Zertifikat für mail.die-udes.de mit dem aktuellem Timestamp als abgelaufen aktualisiert. Im Log finde ich unter anderem:

Found AAAA record for mail.die-udes.de: fd4d:6169:6c63:6f77::13 - skipping A record check
Cannot match your IP 2a01:04f8:0c0c:d23c:0000:0000:0000:0001 against hostname mail.die-udes.de (DNS returned fd4d:6169:6c63:6f77:0000:0000:0000:0013)

Das die IPv6-Adresse nicht zu verifizieren ist, ist klar (ist die interne aus mailcow.conf). Aber warum nimmt er die interne und warum wird der A-Record (IPv4) übersprungen?
Ich finde gerade keinen Ansatz wie ich an das Problem weiter ran gehen soll, aber ich habe die mailcow schon aktualisiert, die Docker-Container runter/rauf gefahren und auch schon mal den ganzen Server neugestartet.
Eigentlich ist die mailcow Konfiguration Standard, bis auf die nextcloud.Erweiterung, die dann nach einer Weile auch nicht mehr ging (hier vermute ich zu viele Anfragen bei let’s-Encrypt, sollte sich also mit abwarten von alleine lösen).
Kann mir wer helfen? Was braucht Ihr noch an Informationen?

Danke für Eure Hilfe, Claus-Christian Ude

Anbei schon einmal meine mailcow.conf
# ------------------------------
# mailcow web ui configuration
# ------------------------------
# example.org is _not_ a valid hostname, use a fqdn here.
# Default admin user is "admin"
# Default password is "moohoo"

MAILCOW_HOSTNAME=mail.die-udes.de

# ------------------------------
# SQL database configuration
# ------------------------------

DBNAME=xxxxxx
DBUSER=xxxxxx

# Please use long, random alphanumeric strings (A-Za-z0-9)

DBPASS=xxx
DBROOT=xxx

# ------------------------------
# HTTP/S Bindings
# ------------------------------

# You should use HTTPS, but in case of SSL offloaded reverse proxies:
# Might be important: This will also change the binding within the container.
# If you use a proxy within Docker, point it to the ports you set below.
# Do _not_ use IP:PORT in HTTP(S)_BIND or HTTP(S)_PORT
# IMPORTANT: Do not use port 8081, 9081 or 65510!

HTTP_PORT=80
HTTP_BIND=0.0.0.0

HTTPS_PORT=443
HTTPS_BIND=0.0.0.0

# ------------------------------
# Other bindings
# ------------------------------
# You should leave that alone
# Format: 11.22.33.44:25 or 0.0.0.0:465 etc.

SMTP_PORT=25
SMTPS_PORT=465
SUBMISSION_PORT=587
IMAP_PORT=143
IMAPS_PORT=993
POP_PORT=110
POPS_PORT=995
SIEVE_PORT=4190
DOVEADM_PORT=127.0.0.1:19991
SQL_PORT=127.0.0.1:13306
SOLR_PORT=127.0.0.1:18983
REDIS_PORT=127.0.0.1:7654

# Your timezone

TZ=Europe/Berlin

# Fixed project name
# Please use lowercase letters only

COMPOSE_PROJECT_NAME=mailcowdockerized

# Set this to "allow" to enable the anyone pseudo user. Disabled by default.
# When enabled, ACL can be created, that apply to "All authenticated users"
# This should probably only be activated on mail hosts, that are used exclusivly by one organisation.
# Otherwise a user might share data with too many other users.
ACL_ANYONE=disallow

# Garbage collector cleanup
# Deleted domains and mailboxes are moved to /var/vmail/_garbage/timestamp_sanitizedstring
# How long should objects remain in the garbage until they are being deleted? (value in minutes)
# Check interval is hourly

MAILDIR_GC_TIME=7200

# Additional SAN for the certificate
#
# You can use wildcard records to create specific names for every domain you add to mailcow.
# Example: Add domains "example.com" and "example.net" to mailcow, change ADDITIONAL_SAN to a value like:
#ADDITIONAL_SAN=imap.*,smtp.*
# This will expand the certificate to "imap.example.com", "smtp.example.com", "imap.example.net", "imap.example.net"
# plus every domain you add in the future.
#
# You can also just add static names...
#ADDITIONAL_SAN=srv1.example.net
# ...or combine wildcard and static names:
#ADDITIONAL_SAN=imap.*,srv1.example.com
#

#ADDITIONAL_SAN=mail.die-udes.de,nextcloud.die-udes.de,helft-leonard.de
#ADDITIONAL_SAN=*.die-udes.de

# Skip running ACME (acme-mailcow, Let's Encrypt certs) - y/n

SKIP_LETS_ENCRYPT=n

# Create seperate certificates for all domains - y/n
# this will allow adding more than 100 domains, but some email clients will not be able to connect with alternative hostnames
# see https://wiki.dovecot.org/SSL/SNIClientSupport
ENABLE_SSL_SNI=n

# Skip IPv4 check in ACME container - y/n

SKIP_IP_CHECK=n

# Skip HTTP verification in ACME container - y/n

SKIP_HTTP_VERIFICATION=n

# Skip ClamAV (clamd-mailcow) anti-virus (Rspamd will auto-detect a missing ClamAV container) - y/n

SKIP_CLAMD=n

# Skip SOGo: Will disable SOGo integration and therefore webmail, DAV protocols and ActiveSync support (experimental, unsupported, not fully implemented) - y/n

SKIP_SOGO=n

# Skip Solr on low-memory systems or if you do not want to store a readable index of your mails in solr-vol-1.

SKIP_SOLR=n

# Solr heap size in MB, there is no recommendation, please see Solr docs.
# Solr is a prone to run OOM and should be monitored. Unmonitored Solr setups are not recommended.

SOLR_HEAP=1024

# Allow admins to log into SOGo as email user (without any password)

ALLOW_ADMIN_EMAIL_LOGIN=n

# Enable watchdog (watchdog-mailcow) to restart unhealthy containers

USE_WATCHDOG=y

# Send watchdog notifications by mail (sent from watchdog@MAILCOW_HOSTNAME)
# CAUTION:
# 1. You should use external recipients
# 2. Mails are sent unsigned (no DKIM)
# 3. If you use DMARC, create a separate DMARC policy ("v=DMARC1; p=none;" in _dmarc.MAILCOW_HOSTNAME)
# Multiple rcpts allowed, NO quotation marks, NO spaces

#WATCHDOG_NOTIFY_EMAIL=a@example.com,b@example.com,c@example.com
#WATCHDOG_NOTIFY_EMAIL=

# Notify about banned IP (includes whois lookup)
WATCHDOG_NOTIFY_BAN=n

# Checks if mailcow is an open relay. Requires a SAL. More checks will follow.
# https://www.servercow.de/mailcow?lang=en
# https://www.servercow.de/mailcow?lang=de
# No data is collected. Opt-in and anonymous.
# Will only work with unmodified mailcow setups.
WATCHDOG_EXTERNAL_CHECKS=n

# Max log lines per service to keep in Redis logs

LOG_LINES=9999

# Internal IPv4 /24 subnet, format n.n.n (expands to n.n.n.0/24)
# Use private IPv4 addresses only, see https://en.wikipedia.org/wiki/Private_network#Private_IPv4_addresses

IPV4_NETWORK=172.22.1

# Internal IPv6 subnet in fc00::/7
# Use private IPv6 addresses only, see https://en.wikipedia.org/wiki/Private_network#Private_IPv6_addresses

IPV6_NETWORK=fd4d:6169:6c63:6f77::/64

# Use this IPv4 for outgoing connections (SNAT)

#SNAT_TO_SOURCE=

# Use this IPv6 for outgoing connections (SNAT)

#SNAT6_TO_SOURCE=

# Create or override an API key for the web UI
# You _must_ define API_ALLOW_FROM, which is a comma separated list of IPs
# An API key defined as API_KEY has read-write access
# An API key defined as API_KEY_READ_ONLY has read-only access
# Allowed chars for API_KEY and API_KEY_READ_ONLY: a-z, A-Z, 0-9, -
# You can define API_KEY and/or API_KEY_READ_ONLY

#API_KEY=
#API_KEY_READ_ONLY=
#API_ALLOW_FROM=172.22.1.1,127.0.0.1

# mail_home is ~/Maildir
MAILDIR_SUB=Maildir

# SOGo session timeout in minutes
SOGO_EXPIRE_SESSION=480

# DOVECOT_MASTER_USER and DOVECOT_MASTER_PASS must both be provided. No special chars.
# Empty by default to auto-generate master user and password on start.
# User expands to DOVECOT_MASTER_USER@mailcow.local
# LEAVE EMPTY IF UNSURE
DOVECOT_MASTER_USER=
# LEAVE EMPTY IF UNSURE
DOVECOT_MASTER_PASS=