IMAP Connection Timeout after migration to Bare-Metal Installation

[hakunamatata]

Environment:

• Hardware: Mini PC (Bare-metal)
• OS: Ubuntu 24.04.4
• Cloudron Version: 9.1.3
• Internal IP: 10.69.69.69
• Router/DNS/Firewall IP: 10.69.69.1
• Cloudron Mailserver: my.domain.tld

Problem Description:
I recently migrated my Cloudron installation from a Synology VM to a bare-metal install. Since then, Paperless-ngx cannot connect to the internal Cloudron Mail server via the public FQDN (my.domain.tld) to ingest email attachments for processing.

Diagnostics:

• nc -zv 10.69.69.69 993 from the app terminal succeeds.
• nc -zv my.domain.tld 993 from the app terminal does not receive any response.
• Per the paperless mail.log [ERROR] [paperless_mail] Error while retrieving mailbox Paperless: [Errno 110] Connection timed out.
• Inside the container, the domain resolves to the Public IP rather than the local IP, leading to a loopback failure on my UniFi UDM SE.
• Attempts to override this via /etc/unbound/unbound.conf.d/custom.conf have not been successful in getting the container to prioritize the local IP.

# Forward all queries to the network's internal DNS 10.69.69.1. 
forward-zone:
  name: "."
  forward-addr: 10.69.69.1

Request:
What is the recommended Cloudron-native way to force apps to resolve the Mail server to the local host IP (10.69.69.69) to avoid Hairpin NAT issues, specifically for a bare-metal installation?

Note:
I already have a local DNS A record set up on the Unifi UDM SE that points the local IP (10.69.69.69) to domain.tld.

[hakunamatata]

Disregard, it was a firewall issue on my DMZ VLAN. Please close/delete this topic.

[hakunamatata]

@joseph quick question, does the cloudron backup include the custom.conf file if it exists on the server?

[joseph]

Backup does not contain the unbound custom.conf .

[robi]

@hakunamatata only things in /app/data