Merge #1398

1398: Update crypto to be modern and inline with tls.conf r=mergify[bot] a=bladeswords

Updated to match tls.conf and be aligned to more modern cryptographic standards and only use currently secure protocols and ciphers.

## What type of PR?

bugfix

## What does this PR do?
Update to use more modern cryptographic techniques
### Related issue(s)
- Addresses comment raised in 4f973f6

## Prerequistes
None


Co-authored-by: bladeswords <bladeswords@users.noreply.github.com>

core/nginx/conf/nginx.conf

@@ -218,9 +218,9 @@ mail {
       listen 25;
       listen [::]:25;
       {% if TLS and not TLS_ERROR %}
-      ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
+      ssl_protocols TLSv1.2 TLSv1.3;
-      ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA;
+      ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384;
-      ssl_prefer_server_ciphers on;
+      ssl_prefer_server_ciphers off;
       starttls on;
       {% endif %}
       protocol smtp;