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Hey everyone :) I'm experimenting with my Raspberry Pi to set it up as a mail server. I'm using dynv6.net as dynamic DNS Provider for IPv6 only, since i only have Dual Stack Lite at home. The nececcary ports for the email-server are open. And i can send e-mails to anyadress@mail.de through the Pi (uses IPv6) which arrive just fine. But i can't receive any Emails from outside. The DNS MX record is set for that domain. I don't receive any errors from my email provider so far. Can you please help me to find the mistake? Here is my main.cf from postfix:

    ## See /usr/share/postfix/main.cf.dist for a commented, more complete version

inet_protocols = ipv6

# Debian specific:  Specifying a file name will cause the first
# line of that file to be used as the name.  The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Raspbian)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# See http://www.postfix.org/COMPATIBILITY_README.html -- default to 2 on
# fresh installs.
compatibility_level = 2

# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/emailserv.crt
smtpd_tls_key_file=/etc/ssl/private/emailserv.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_tls_received_header = yes
smtpd_tls_mandatory_protocols = SSLv3, TLSv1
smtpd_tls_mandatory_ciphers = medium
smtpd_tls_auth_only = yes
tls_random_source = dev:/dev/urandom


# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = Kaito-RasPi
mydomain = futuregadgetlab.dynv6.net
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = $myhostname, Kaito-RasPi, localhost.localdomain, localhost, futuregadgetlab.dynv6.net
#relayhost = 
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
#inet_protocols = all
home_mailbox = Maildir/
smtpd_sasl_auth_enable = yes
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/dovecot-auth
smtpd_sasl_authenticated_header = yes
smtpd_sasl_local_domain = $myhostname
broken_sasl_auth_clients = yes
smtpd_recipient_restrictions = reject_unknown_sender_domain reject_unknown_recipient_domain reject_unauth_pipelining permit_mynetworks permit_sasl_authenticated reject_unauth_destination
smtpd_sender_restrictions = reject_unknown_sender_domain permit_sasl_authenticated
mailbox_command = /usr/lib/dovecot/deliver -c /etc/dovecot/conf.d/01-mail-stack-delivery.conf -m "${EXTENSION}"
virtual_alias_maps = hash:/etc/postfix/virtual

and here master.cf:

    #
# Postfix master process configuration file.  For details on the format
# of the file, see the master(5) manual page (command: "man 5 master" or
# on-line: http://www.postfix.org/master.5.html).
#
# Do not forget to execute "postfix reload" after editing this file.
#
# ==========================================================================
# service type  private unpriv  chroot  wakeup  maxproc command + args
#               (yes)   (yes)   (no)    (never) (100)
# ==========================================================================
smtp      inet  n       -       y       -       -       smtpd
smtps     inet  n   -   y   -   -   smtpd
#smtp      inet  n       -       y       -       1       postscreen
#smtpd     pass  -       -       y       -       -       smtpd
#dnsblog   unix  -       -       y       -       0       dnsblog
#tlsproxy  unix  -       -       y       -       0       tlsproxy
submission inet n       -       y       -       -       smtpd
#  -o syslog_name=postfix/submission
#  -o smtpd_tls_security_level=encrypt
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_reject_unlisted_recipient=no
#  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#  -o smtpd_helo_restrictions=$mua_helo_restrictions
#  -o smtpd_sender_restrictions=$mua_sender_restrictions
#  -o smtpd_recipient_restrictions=
#  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING
#smtps     inet  n       -       y       -       -       smtpd
#  -o syslog_name=postfix/smtps
#  -o smtpd_tls_wrappermode=yes
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_reject_unlisted_recipient=no
#  -o smtpd_client_restrictions=$mua_client_restrictions
#  -o smtpd_helo_restrictions=$mua_helo_restrictions
#  -o smtpd_sender_restrictions=$mua_sender_restrictions
#  -o smtpd_recipient_restrictions=
#  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING
#628       inet  n       -       y       -       -       qmqpd
pickup    unix  n       -       y       60      1       pickup
cleanup   unix  n       -       y       -       0       cleanup
qmgr      unix  n       -       n       300     1       qmgr
#qmgr     unix  n       -       n       300     1       oqmgr
tlsmgr    unix  -       -       y       1000?   1       tlsmgr
rewrite   unix  -       -       y       -       -       trivial-rewrite
bounce    unix  -       -       y       -       0       bounce
defer     unix  -       -       y       -       0       bounce
trace     unix  -       -       y       -       0       bounce
verify    unix  -       -       y       -       1       verify
flush     unix  n       -       y       1000?   0       flush
proxymap  unix  -       -       n       -       -       proxymap
proxywrite unix -       -       n       -       1       proxymap
smtp      unix  -       -       y       -       -       smtp
relay     unix  -       -       y       -       -       smtp
#       -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
showq     unix  n       -       y       -       -       showq
error     unix  -       -       y       -       -       error
retry     unix  -       -       y       -       -       error
discard   unix  -       -       y       -       -       discard
local     unix  -       n       n       -       -       local
virtual   unix  -       n       n       -       -       virtual
lmtp      unix  -       -       y       -       -       lmtp
anvil     unix  -       -       y       -       1       anvil
scache    unix  -       -       y       -       1       scache
#
# ====================================================================
# Interfaces to non-Postfix software. Be sure to examine the manual
# pages of the non-Postfix software to find out what options it wants.
#
# Many of the following services use the Postfix pipe(8) delivery
# agent.  See the pipe(8) man page for information about ${recipient}
# and other message envelope options.
# ====================================================================
#
# maildrop. See the Postfix MAILDROP_README file for details.
# Also specify in main.cf: maildrop_destination_recipient_limit=1
#
maildrop  unix  -       n       n       -       -       pipe
  flags=DRhu user=vmail argv=/usr/bin/maildrop -d ${recipient}
#
# ====================================================================
#
# Recent Cyrus versions can use the existing "lmtp" master.cf entry.
#
# Specify in cyrus.conf:
#   lmtp    cmd="lmtpd -a" listen="localhost:lmtp" proto=tcp4
#
# Specify in main.cf one or more of the following:
#  mailbox_transport = lmtp:inet:localhost
#  virtual_transport = lmtp:inet:localhost
#
# ====================================================================
#
# Cyrus 2.1.5 (Amos Gouaux)
# Also specify in main.cf: cyrus_destination_recipient_limit=1
#
#cyrus     unix  -       n       n       -       -       pipe
#  user=cyrus argv=/cyrus/bin/deliver -e -r ${sender} -m ${extension} ${user}
#
# ====================================================================
# Old example of delivery via Cyrus.
#
#old-cyrus unix  -       n       n       -       -       pipe
#  flags=R user=cyrus argv=/cyrus/bin/deliver -e -m ${extension} ${user}
#
# ====================================================================
#
# See the Postfix UUCP_README file for configuration details.
#
uucp      unix  -       n       n       -       -       pipe
  flags=Fqhu user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
#
# Other external delivery methods.
#
ifmail    unix  -       n       n       -       -       pipe
  flags=F user=ftn argv=/usr/lib/ifmail/ifmail -r $nexthop ($recipient)
bsmtp     unix  -       n       n       -       -       pipe
  flags=Fq. user=bsmtp argv=/usr/lib/bsmtp/bsmtp -t$nexthop -f$sender $recipient
scalemail-backend unix  -   n   n   -   2   pipe
  flags=R user=scalemail argv=/usr/lib/scalemail/bin/scalemail-store ${nexthop} ${user} ${extension}
mailman   unix  -       n       n       -       -       pipe
  flags=FR user=list argv=/usr/lib/mailman/bin/postfix-to-mailman.py
  ${nexthop} ${user}
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  • Have you tested mails from other providers? It might be that the provider you have tested with just doesn't support sending over IPv6 yet. If you mentioned the domain name we'd be able to look at just how you have configured your DNS records and tell you if there is any problem with them. – kasperd Oct 8 '17 at 22:52
  • I haven't come across many IPv6-capable providers yet. I've set up another server (IPv6-only, same config as above) at my friends home to test sending from there, works if i send to mail.de ut not my own mailserver. Domain of my own webserver: futuregadgetlab.dynv6.net – KaitoCross Oct 9 '17 at 4:31
  • And what is the domain you want to receive mail for? – Sander Steffann Oct 9 '17 at 6:25
  • i want to receive emails on and for futuregadgetlab.dynv6.net, which is my raspberry pi. the friend's server is lernsquad.dynv6.net, which is currently offline. – KaitoCross Oct 9 '17 at 6:50
  • @KaitoCross The first problem I see is that the authoritative DNS servers for dynv6.net are sending corrupt DNS responses. dig +norecurse mx futuregadgetlab.dynv6.net @ns1.dynv6.net will print the response with a warning. But most recursors will report SERVFAIL when they see the corrupt response. – kasperd Oct 9 '17 at 7:11
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Your problem appears to be that the authoritative DNS servers for dynv6.net are sending corrupt DNS responses. This is what I saw when I first attempted to resolve your MX record:

$ dig mx futuregadgetlab.dynv6.net

; <<>> DiG 9.10.3-P4-Ubuntu <<>> mx futuregadgetlab.dynv6.net
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 7934
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;futuregadgetlab.dynv6.net.     IN      MX

;; Query time: 219 msec
;; SERVER: 127.0.1.1#53(127.0.1.1)
;; WHEN: Mon Oct 09 08:19:58 BST 2017
;; MSG SIZE  rcvd: 54

I have tested a few different recursors which all gave me the same SERVFAIL response. Systems trying to send mails to the domain will queue mails until that problem gets fixed (and if the problem persists for a few days the mails will bounce).

In order to find out why I got a SERVFAIL response I did the lookups manually starting from the root and working my way down. When I got to ns1.dynv6.net I got this warning about corrupt DNS response packets.

$ dig +norecurse mx futuregadgetlab.dynv6.net @ns1.dynv6.net
;; Warning: Message parser reports malformed message packet.

; <<>> DiG 9.10.3-P4-Ubuntu <<>> +norecurse mx futuregadgetlab.dynv6.net @ns1.dynv6.net
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 25407
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: Message has 2 extra bytes at end

;; QUESTION SECTION:
;futuregadgetlab.dynv6.net.     IN      MX

;; Query time: 19 msec
;; SERVER: 2a03:4000:10:1db::#53(2a03:4000:10:1db::)
;; WHEN: Mon Oct 09 08:23:22 BST 2017
;; MSG SIZE  rcvd: 82

Until the DNS servers for dynv6.net are fixed you shouldn't expect any legitimate email to be getting through. The problem appears to be only affecting MX lookups. At least A and AAAA lookups works fine. And connecting to port 25 on the address from the AAAA lookup also works.

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  • For what it's worth, the A record also fails for me. No MX or A records, but a valid AAAA record, would explain why nothing v4 can send email, but at least some v6-capable apps (ie, those which are clever enough to fall back to an AAAA record in the absence of MX) can do so. – MadHatter Oct 9 '17 at 8:51
  • There is no A record on purpose since i don't have my own IPv4 for my household, i'm sitting behind a carrier grade NAT that controls IPv4 access. – KaitoCross Oct 9 '17 at 10:44
  • @MadHatter There is a difference between the lookup failing and the lookup reporting that there is no record. Which of the two did you see in each case? – kasperd Oct 9 '17 at 19:39
  • I agree. In the case of the MX record, failure as you saw. In the case of the A record, no record returned, unlike what you saw (assuming that "A lookup works fine" means that you got a record). – MadHatter Oct 9 '17 at 22:40
  • @KaitoCross hang on, are you saying that you knew that you had no ipv4 address, and yet you're surprised that you only got mail from v6-capable servers? – MadHatter Oct 9 '17 at 22:42

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