SSL enabled SMTP Stream drops connection

Checklist

• Have you pulled and found the error with jc21/nginx-proxy-manager:latest docker image?
  • Yes / No - Yes
• Are you sure you're not using someone else's docker image?
  • Yes / No - Yes
• Have you searched for similar issues (both open and closed)?
  • Yes / No - Yes, extensive troubleshooting and research with AI tools

Describe the bug

Trying to set up a Stream for SMTP relay (Port 465) doesn't work as expected. NPM doesn't properly complete SMTP handshake with SSL and drops connection. Initial connection establishes, but no EHLO response happens and the connection drops. SMTP connection works when SSL disabled for the Stream. SMTP connection also confirmed to work over SSL when bypassing NPM (router - port 465 forwarded directly to SMTP server).

Nginx Proxy Manager Version

2.12.3

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

1. Set up SSL enabled Stream for Port 465 (or other port) pointed to SMTP server
2. Router - Port forward 465 to NPM
3. Attempt SMTP+SSL connection from any machine.

Expected behavior

SMTP+SSL works.

Screenshots

Operating System

SMTP Server running off of cPanel 126.0.16 / Alma Linux v9.5.0
NPM running in Docker container with all necessary Ports for SMTP as well as HTTP/HTTPS opened

Additional context

Reason this needs to be fixed:
Need Secure SMTP to be able to verify SSL certificate from NPM Stream. Because Stream doesn't work, self-signed cert on SMTP server is configured and unable leverage NPM SSL cert.

The issue names no source files, tests, or implementation entry points. Start by reproducing the SSL-enabled Stream on port 465 with Nginx Proxy Manager 2.12.3 and inspect the SMTP handshake and container logs. Done means SMTP over SSL completes through the Stream and the existing direct-to-server behavior remains unaffected.