DKIM not working for external alias emails

[zehweh]

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Description

Hi all,

first of all: Thanks for this great piece of software!

Now to my problem: When using external email addresses for aliases, DKIM naturally doesn't work.

Example: [email protected] wants to send an email to [email protected] (running on 111.111.111.111 with goto address: [email protected], [email protected], [email protected])

mx.test.com is running on 222.222.222.222

1st SPF check by MX at mailcow-server.com: spf=pass (mail.mailcow-server.com: domain of [email protected] designates 222.222.222.222 as permitted sender) 2nd SPF check by MX at recipient.com: spf=fail (mail.recipient.com: domain of [email protected] does not designate 111.111.111.111 as permitted sender)

I looked into how google solves this with their "Groups" feature. They seems to circumvent this issue modifying the Return-Path header like: Return-Path: [email protected] so that the recieving MX verifies SPF using this email address.

Would it be possible to do the same with mailcow?

Thanks, chris

Logs

No logs, just email headers...

Steps to reproduce

1. Create an alias email, like [email protected]
2. Add external email addresses as goto address, like one@recipient, two@recipient, three@recipient
3. Send an email to [email protected] from @someotherdomain.com and check the headers of one of the recipients.

System information

Question	Answer
My operating system	Ubuntu 20.04
Is Apparmor, SELinux or similar active?	No
Virtualization technology (KVM, VMware, Xen, etc - LXC and OpenVZ are not supported	KVM
Server/VM specifications (Memory, CPU Cores)	8GB RAM, 4 Cores
Docker version (docker version)	19.03.14
docker-compose version (docker-compose version)	1.29.2
mailcow version (git describe --tags `git rev-list --tags --max-count=1` )	2022-05a
Reverse proxy (custom solution)	only web: nginx

DNS problems? Please run docker exec -it $(docker ps -qf name=acme-mailcow) dig +short stackoverflow.com @172.22.1.254 (set the IP accordingly, if you changed the internal mailcow network) and post the output:

151.101.193.69
151.101.65.69
151.101.129.69
151.101.1.69