Mail delivery failed bounce back responses to spam mails

[007hacky007]

Describe the bug

My Postal instance is generating large amounts of bounce back "Mail delivery failed" responses to incoming spam e-mails. It started doing so after upgrading from 2.1.2 to 2.1.4.

To Reproduce

Upgrade/run latest version (2.1.4) and see "Mail delivery failed" responses generated automatically by Postal - which is confirmed by "Unknown Credential" in the outgoing message detail.

Expected behaviour

No response to incoming spam messages. Just mark them as spam and do not respond to them at all - the behavior of the 2.1.2 version.

I'm happy to provide more debug information if required.

Screenshots

Environment details

postal :: ~ 1 » cat /etc/debian_version
11.7
postal :: ~ » docker version
Client:
 Version:           20.10.5+dfsg1
 API version:       1.41
 Go version:        go1.15.15
 Git commit:        55c4c88
 Built:             Mon May 30 18:34:49 2022
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server:
 Engine:
  Version:          20.10.5+dfsg1
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.15.15
  Git commit:       363e9a8
  Built:            Mon May 30 18:34:49 2022
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.4.13~ds1
  GitCommit:        1.4.13~ds1-1~deb11u4
 runc:
  Version:          1.0.0~rc93+ds1
  GitCommit:        1.0.0~rc93+ds1-5+deb11u2
 docker-init:
  Version:          0.19.0
  GitCommit:
postal :: ~ » postal status
NAME                IMAGE                               COMMAND                  SERVICE             CREATED             STATUS              PORTS
postal-cron-1       ghcr.io/postalserver/postal:2.1.4   "/docker-entrypoint.…"   cron                6 days ago          Up 6 days
postal-requeuer-1   ghcr.io/postalserver/postal:2.1.4   "/docker-entrypoint.…"   requeuer            6 days ago          Up 6 days
postal-smtp-1       ghcr.io/postalserver/postal:2.1.4   "/docker-entrypoint.…"   smtp                6 days ago          Up 6 days
postal-web-1        ghcr.io/postalserver/postal:2.1.4   "/docker-entrypoint.…"   web                 6 days ago          Up 6 days
postal-worker-1     ghcr.io/postalserver/postal:2.1.4   "/docker-entrypoint.…"   worker              6 days ago          Up 6 days
postal :: ~ »