mailcow-dockerized 'whitelisting postmaster smtp rcpt'-Rule disables DKIM-signing outbound mails to postmaster recipients

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Description

When sending outbound mails from a mailcow instance to a postmaster recipient, the current whitelisting rule in rspamd skips DKIM signing the mail. This could lead to bad reputation of the outbound mail due to a missing signature.

Logs:

rspamd-mailcow-1  | 2024-04-02 12:06:37 #42(normal) <7129ae>; task; rspamd_task_write_log: id: <cefe5303-0299-44e5-b198-8e37a5d5b84e@[owndomain].info>, qid: <947D2102981>, ip: X.X.X.X, user: kevin@[owndomain].info, from: <kevin@[owndomain].info>, (default: F (no action): [0.00/15.00] [DYN_RL_CHECK(0.00){}]), len: 374, time: 2.275ms, dns req: 0, digest: <ea90c6d0f528db497e6093baea37e62b>, rcpts: <postmaster@[externaldomain].de>, mime_rcpts: <postmaster@[externaldomain].de>, forced: no action "whitelisting postmaster smtp rcpt"; score=nan (set by Unknown lua)

Steps to reproduce:

1. Sending a mail from a dkim-enabled domain from within mailcow (either by a client or via SoGo doesn't matter) to any external postmaster@... recipient.
2. rspamd skips this mail by "whitelisting postmaster smtp rcpt"
2. Check in external postmaster mailbox that mail has no DKIM signature

Which branch are you using?

master

Which architecture are you using?

x86

Operating System:

Ubuntu 22.04.4 LTS

Server/VM specifications:

VM, 8GB/6 Cores

Is Apparmor, SELinux or similar active?

no

Virtualization technology:

KVM

Docker version:

26.0.0

docker-compose version or docker compose version:

v2.25.0

mailcow version:

2024-02

Reverse proxy:

Nginx

Logs of git diff:

None (except ssh-key and IP/port in create_cold_standby.sh)

Logs of iptables -L -vn:

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain FORWARD (policy DROP 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
  18M 4956M MAILCOW    all  --  *      *       0.0.0.0/0            0.0.0.0/0            /* mailcow */
  18M 4956M DOCKER-USER  all  --  *      *       0.0.0.0/0            0.0.0.0/0           
  18M 4956M DOCKER-ISOLATION-STAGE-1  all  --  *      *       0.0.0.0/0            0.0.0.0/0           
    0     0 ACCEPT     all  --  *      docker0  0.0.0.0/0            0.0.0.0/0            ctstate RELATED,ESTABLISHED
    0     0 DOCKER     all  --  *      docker0  0.0.0.0/0            0.0.0.0/0           
    0     0 ACCEPT     all  --  docker0 !docker0  0.0.0.0/0            0.0.0.0/0           
    0     0 ACCEPT     all  --  docker0 docker0  0.0.0.0/0            0.0.0.0/0           
  14M 2166M ACCEPT     all  --  *      br-mailcow  0.0.0.0/0            0.0.0.0/0            ctstate RELATED,ESTABLISHED
1385K   87M DOCKER     all  --  *      br-mailcow  0.0.0.0/0            0.0.0.0/0           
3048K 2702M ACCEPT     all  --  br-mailcow !br-mailcow  0.0.0.0/0            0.0.0.0/0           
1363K   86M ACCEPT     all  --  br-mailcow br-mailcow  0.0.0.0/0            0.0.0.0/0           

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain DOCKER (2 references)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.4           tcp dpt:3306
    0     0 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.249         tcp dpt:6379
    0     0 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.7           tcp dpt:8983
 5064  330K ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.9           tcp dpt:443
 2212  122K ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.9           tcp dpt:80
10245  649K ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.253         tcp dpt:587
  505 29412 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.253         tcp dpt:465
  749 40504 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.253         tcp dpt:25
    0     0 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.250         tcp dpt:12345
   20  1088 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.250         tcp dpt:4190
  527 30716 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.250         tcp dpt:995
 1591 93411 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.250         tcp dpt:993
  322 18344 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.250         tcp dpt:143
  342 19656 ACCEPT     tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            172.22.1.250         tcp dpt:110

Chain DOCKER-ISOLATION-STAGE-1 (1 references)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 DOCKER-ISOLATION-STAGE-2  all  --  docker0 !docker0  0.0.0.0/0            0.0.0.0/0           
3048K 2702M DOCKER-ISOLATION-STAGE-2  all  --  br-mailcow !br-mailcow  0.0.0.0/0            0.0.0.0/0           
  18M 4956M RETURN     all  --  *      *       0.0.0.0/0            0.0.0.0/0           

Chain DOCKER-ISOLATION-STAGE-2 (2 references)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 DROP       all  --  *      docker0  0.0.0.0/0            0.0.0.0/0           
    0     0 DROP       all  --  *      br-mailcow  0.0.0.0/0            0.0.0.0/0           
3048K 2702M RETURN     all  --  *      *       0.0.0.0/0            0.0.0.0/0           

Chain DOCKER-USER (1 references)
 pkts bytes target     prot opt in     out     source               destination         
  18M 4956M RETURN     all  --  *      *       0.0.0.0/0            0.0.0.0/0           

Chain MAILCOW (1 references)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 DROP       tcp  --  !br-mailcow br-mailcow  0.0.0.0/0            0.0.0.0/0            /* mailcow isolation */

Logs of ip6tables -L -vn:

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
3210K  823M MAILCOW    all      *      *       ::/0                 ::/0                 /* mailcow */
3210K  823M DOCKER-USER  all      *      *       ::/0                 ::/0                
3044K  805M DOCKER     all      *      br-mailcow  ::/0                 ::/0                
2582K  769M ACCEPT     all      *      br-mailcow  ::/0                 ::/0                 ctstate RELATED,ESTABLISHED
 165K   18M ACCEPT     all      br-mailcow !br-mailcow  ::/0                 ::/0                
 457K   33M ACCEPT     all      br-mailcow br-mailcow  ::/0                 ::/0                
  769 65700 DOCKER-ISOLATION-STAGE-1  all      *      *       ::/0                 ::/0                

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain DOCKER (1 references)
 pkts bytes target     prot opt in     out     source               destination         
  560 63498 ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::c  tcp dpt:443
  445 39755 ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::c  tcp dpt:80
 2835  345K ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::12  tcp dpt:993
  148 19934 ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::12  tcp dpt:995
   34  3254 ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::12  tcp dpt:110
   31  3058 ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::12  tcp dpt:143
    7   492 ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::12  tcp dpt:4190
 1106 1872K ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::11  tcp dpt:25
  247 31798 ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::11  tcp dpt:465
  365  415K ACCEPT     tcp      !br-mailcow br-mailcow  ::/0                 fd4d:6169:6c63:6f77::11  tcp dpt:587

Chain DOCKER-ISOLATION-STAGE-1 (1 references)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 DOCKER-ISOLATION-STAGE-2  all      br-mailcow !br-mailcow  ::/0                 ::/0                
  769 65700 RETURN     all      *      *       ::/0                 ::/0                

Chain DOCKER-ISOLATION-STAGE-2 (1 references)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 DROP       all      *      br-mailcow  ::/0                 ::/0                
    0     0 RETURN     all      *      *       ::/0                 ::/0                

Chain DOCKER-USER (1 references)
 pkts bytes target     prot opt in     out     source               destination         
3210K  823M RETURN     all      *      *       ::/0                 ::/0                

Chain MAILCOW (1 references)
 pkts bytes target     prot opt in     out     source               destination

Logs of iptables -L -vn -t nat:

Chain PREROUTING (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
 239K   12M DOCKER     all  --  *      *       0.0.0.0/0            0.0.0.0/0            ADDRTYPE match dst-type LOCAL

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 DOCKER     all  --  *      *       0.0.0.0/0           !127.0.0.0/8          ADDRTYPE match dst-type LOCAL

Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 MASQUERADE  all  --  *      !docker0  172.17.0.0/16        0.0.0.0/0           
 838K   62M MASQUERADE  all  --  *      !br-mailcow  172.22.1.0/24        0.0.0.0/0           
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.4           172.22.1.4           tcp dpt:3306
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.249         172.22.1.249         tcp dpt:6379
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.7           172.22.1.7           tcp dpt:8983
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.9           172.22.1.9           tcp dpt:443
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.9           172.22.1.9           tcp dpt:80
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.253         172.22.1.253         tcp dpt:587
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.253         172.22.1.253         tcp dpt:465
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.253         172.22.1.253         tcp dpt:25
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.250         172.22.1.250         tcp dpt:12345
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.250         172.22.1.250         tcp dpt:4190
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.250         172.22.1.250         tcp dpt:995
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.250         172.22.1.250         tcp dpt:993
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.250         172.22.1.250         tcp dpt:143
    0     0 MASQUERADE  tcp  --  *      *       172.22.1.250         172.22.1.250         tcp dpt:110

Chain DOCKER (2 references)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 RETURN     all  --  docker0 *       0.0.0.0/0            0.0.0.0/0           
   26  1560 RETURN     all  --  br-mailcow *       0.0.0.0/0            0.0.0.0/0           
    0     0 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            127.0.0.1            tcp dpt:13306 to:172.22.1.4:3306
    0     0 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            127.0.0.1            tcp dpt:7654 to:172.22.1.249:6379
    0     0 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            127.0.0.1            tcp dpt:18983 to:172.22.1.7:8983
 5061  330K DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:443 to:172.22.1.9:443
 2212  122K DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:80 to:172.22.1.9:80
10241  648K DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:587 to:172.22.1.253:587
  505 29412 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:465 to:172.22.1.253:465
  752 40684 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:25 to:172.22.1.253:25
    0     0 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            127.0.0.1            tcp dpt:19991 to:172.22.1.250:12345
   20  1088 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:4190 to:172.22.1.250:4190
  527 30716 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:995 to:172.22.1.250:995
 1591 93411 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:993 to:172.22.1.250:993
  322 18344 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:143 to:172.22.1.250:143
  342 19656 DNAT       tcp  --  !br-mailcow *       0.0.0.0/0            0.0.0.0/0            tcp dpt:110 to:172.22.1.250:110

Logs of ip6tables -L -vn -t nat:

Chain PREROUTING (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
 1334 94472 DOCKER     all      *      *       ::/0                 ::/0                 ADDRTYPE match dst-type LOCAL

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 DOCKER     all      *      *       ::/0                !::1                  ADDRTYPE match dst-type LOCAL

Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 MASQUERADE  all      *      br-mailcow  ::/0                 ::/0                 ADDRTYPE match dst-type LOCAL
 158K   15M MASQUERADE  all      *      !br-mailcow  fd4d:6169:6c63:6f77::/64  ::/0                
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::c  fd4d:6169:6c63:6f77::c  tcp dpt:443
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::c  fd4d:6169:6c63:6f77::c  tcp dpt:80
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::12  fd4d:6169:6c63:6f77::12  tcp dpt:993
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::12  fd4d:6169:6c63:6f77::12  tcp dpt:995
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::12  fd4d:6169:6c63:6f77::12  tcp dpt:110
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::12  fd4d:6169:6c63:6f77::12  tcp dpt:143
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::12  fd4d:6169:6c63:6f77::12  tcp dpt:4190
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::11  fd4d:6169:6c63:6f77::11  tcp dpt:25
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::11  fd4d:6169:6c63:6f77::11  tcp dpt:465
    0     0 MASQUERADE  tcp      *      *       fd4d:6169:6c63:6f77::11  fd4d:6169:6c63:6f77::11  tcp dpt:587

Chain DOCKER (2 references)
 pkts bytes target     prot opt in     out     source               destination         
   35  2800 RETURN     all      br-mailcow *       ::/0                 ::/0                
   60  4684 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:443 to:[fd4d:6169:6c63:6f77::c]:443
   56  4364 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:80 to:[fd4d:6169:6c63:6f77::c]:80
  147 11728 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:993 to:[fd4d:6169:6c63:6f77::12]:993
   24  1888 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:995 to:[fd4d:6169:6c63:6f77::12]:995
    4   288 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:110 to:[fd4d:6169:6c63:6f77::12]:110
    4   288 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:143 to:[fd4d:6169:6c63:6f77::12]:143
    2   144 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:4190 to:[fd4d:6169:6c63:6f77::12]:4190
   57  4464 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:25 to:[fd4d:6169:6c63:6f77::11]:25
   36  2832 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:465 to:[fd4d:6169:6c63:6f77::11]:465
    7   528 DNAT       tcp      !br-mailcow *       ::/0                 ::/0                 tcp dpt:587 to:[fd4d:6169:6c63:6f77::11]:587

DNS check:

172.64.155.249
104.18.32.7

Apr 02 '24 10:04 gergernaut

That does not only apply to postmaster recipient addresses, it applies also to all outgoing mails from any defined forwarding host, even when spamcheck is on. Thats a pity if you are operating services which send noreply mails, as those are not signed, and can lead even to being blocked.

May 13 '24 16:05 esackbauer

@esackbauer and @gergernaut, if this turns out to be indeed a more widespread issue, then changing the subject of this ticket might be in order. In our case, I can confirm that we're now running 2024-04 and that the last mail that has been signed that I have is from April 10th, whereas the first that is no longer signed is from April 23rd. This gives us only a rough idea when a possible change has happened, but none of the rspamd related commits in that time-span change anything about the current behavior for me.

May 15 '24 15:05 kwisatz

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

Jul 15 '24 00:07 milkmaker

mailcow-dockerized mailcow-dockerized copied to clipboard

'whitelisting postmaster smtp rcpt'-Rule disables DKIM-signing outbound mails to postmaster recipients

Contribution guidelines

I've found a bug and checked that ...

Description

Logs:

Steps to reproduce:

Which branch are you using?

Which architecture are you using?

Operating System:

Server/VM specifications:

Is Apparmor, SELinux or similar active?

Virtualization technology:

Docker version:

docker-compose version or docker compose version:

mailcow version:

Reverse proxy:

Logs of git diff:

Logs of iptables -L -vn:

Logs of ip6tables -L -vn:

Logs of iptables -L -vn -t nat:

Logs of ip6tables -L -vn -t nat:

DNS check:

mailcow-dockerized
mailcow-dockerized copied to clipboard