Tandoor running behind NGINX reverse proxy - SMTP not working

[anthonyuk]

Issue

I'm running Tandoor in a Proxmox container sitting behind NGINX on OPNSense and all is good. Tandoor is natively running HTTP and NGINX is taking care of TLS and LE certs.

I have an issue using Fastmail SMTP in Tandoor and I'm thinking it is related to it sitting behind NGINX.

If I run this command on the Tandoor server I get this error.

openssl s_client -connect smtp.fastmail.com:587 -starttls smtp

4017D5E2867D0000:error:0A000126:SSL routines:ssl3_read_n:unexpected eof while reading:../ssl/record/rec_layer_s3.c:322:

The app says it has sent an email but I can see that the server has never authenticated with fastmail.
I have tried various options which work on my NAS etc and both SSL and TLS (which are required).

Tandoor Version

1.5.30

OS Version

Debian 12

Setup

Others (please state below)

Reverse Proxy

Nginx Proxy Manager (NPM)

Other

Proxmox helper script container

Environment file

# add only a database password if you want to run with the default postgres, otherwise change settings accordingly
DB_ENGINE=django.db.backends.postgresql
POSTGRES_HOST=localhost
POSTGRES_DB=db_recipes
POSTGRES_PORT=5432
POSTGRES_USER=tandoor
POSTGRES_PASSWORD=xxxx
STATIC_URL=/staticfiles/
EMAIL_HOST=smtp.fastmail.com
EMAIL_PORT=587
[email protected]
EMAIL_HOST_PASSWORD=xxxxxxxx
#EMAIL_USE_TLS=0
EMAIL_USE_SSL=1
# email sender address (default 'webmaster@localhost')
[email protected]

Docker-Compose file

Relevant logs