[BUG] SMTP notification fails with "timed out: using smtp" — Gmail 465, works fine with other tools on same host/network

[labob246]

Prerequisites

• I have read the troubleshooting guide

Rclone Pre-flight Checklist (if applicable)

• This issue is NOT related to rclone (skip if not using rclone)
• I have tested rclone listremotes and rclone lsd remote: on the host and they work
• I have verified the rclone config is mounted into the container
• I have restarted the container after config changes

Bug Description

Zerobyte version: v0.41.0 (also reproduced on fresh container + fresh image pull, same appdata DB)
Issue: Email notification test consistently fails with: failed to send: timed out: using smtp
SMTP config: Gmail, smtp.gmail.com:465, TLS enabled, app password (freshly generated, no special characters).

Steps to Reproduce

What I've ruled out:

DNS resolves fine inside the container (nslookup smtp.gmail.com succeeds, both A and AAAA)
Raw TCP connects instantly: nc -zv smtp.gmail.com 465 → open
IPv6 disabled at kernel level (disable_ipv6=1) — no change
Container clock in sync with host
Fully removed/recreated container + re-pulled image — same failure with existing appdata DB
New Gmail app password generated — no change
Tried port 587 (after confirming firewall allows it) — same failure
Uptime Kuma, running on the same Docker host/bridge network, sends successfully with the identical Gmail host/port/TLS/app-password — so it's not network, DNS, firewall, or credential related.

the container has no curl/openssl installed for further manual testing, so I've hit the limit of what I can troubleshoot from inside it.

Expected Behavior

Sends a test email

Zerobyte version / commit

v0.41.0

Deployment Method

Docker

Backup/Repository Context

No response

Logs / Error Messages

failed to send: timed out: using smtp