Issue with SMTP Auth

[tiberios1]

Describe the bug
SMTP Auth is setup but the mailserver isn't using the details. When I try to send, I get an authentication failure which seems to be due to it not even trying to authenticate. This may be a configuration issue on my side, but there isn't clear documentation currently.

To Reproduce
Steps to reproduce the behavior:
add RELAYHOST, RELAY_OPTIONS and RELAY_PASSWD_FILE to the .env file with the relevant values.
eg
RELAYHOST=[smtp.google.com]:587
RELAY_OPTIONS=
RELAY_PASSWD_FILE=/etc/postfix/sasl_passwd

Expected behavior
Able to send emails via smtp auth

Screenshots
If applicable, add screenshots to help explain your problem.

Docker environment (please complete the following information):

• Output of docker info
  Client: Docker Engine - Community
  Version: 27.3.1
  Context: default
  Debug Mode: false
  Plugins:
  buildx: Docker Buildx (Docker Inc.)
  Version: v0.17.1
  Path: /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
  Version: v2.29.7
  Path: /usr/libexec/docker/cli-plugins/docker-compose

Server:
Containers: 27
Running: 27
Paused: 0
Stopped: 0
Images: 117
Server Version: 27.3.1
Storage Driver: overlay2
Backing Filesystem: extfs
Supports d_type: true
Using metacopy: false
Native Overlay Diff: true
userxattr: false
Logging Driver: json-file
Cgroup Driver: systemd
Cgroup Version: 2
Plugins:
Volume: local
Network: bridge host ipvlan macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
Swarm: inactive
Runtimes: io.containerd.runc.v2 runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 7f7fdf5fed64eb6a7caf99b3e12efcf9d60e311c
runc version: v1.1.14-0-g2c9f560
init version: de40ad0
Security Options:
apparmor
seccomp
Profile: builtin
cgroupns
Kernel Version: 6.5.0-25-generic
Operating System: Ubuntu 22.04.5 LTS
OSType: linux
Architecture: x86_64
CPUs: 4
Total Memory: 15.44GiB
Name: Pseudopolisyard
ID: HSQH:AXQJ:7UV3:IC24:7ZQU:A7I5:BHPZ:2NAQ:M7G6:LNIK:QSYT:BBTC
Docker Root Dir: /var/lib/docker
Debug Mode: false
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false

• Output of docker compose version
  Docker Compose version v2.29.7

Additional context
Looking through the commits, I saw that initially smtp_use_tls=yes was set and tried connecting to the mta and running postconf smtp_use_tls=yes. After this was done, the mailserver was authenticating correctly with the relayhost I use.