SMTP not working

[aoor9]

After setting up the server with Podman, behind a NGINX reverse proxy installed in host, I tested mail delivery: while IMAP (993) works, it keeps trying to send messages (port 465) until it blocks my IP address and I have no idea where I did wrong

Here's the logs:

2025-12-06T20:27:55Z INFO Connection error (delivery.connect-error) queueId = 278099417941147919, queueName = "remote", from = "[email protected]", to = ["[email protected]"], size = 1198, total = 1, domain = "gmail.com", hostname = "gmail-smtp-in.l.google.com", localIp = 0.0.0.0, remoteIp = ipv6, remotePort = 25, causedBy = SMTP error occurred (smtp.error) { details = "I/O Error", reason = "Network is unreachable (os error 101)" }, elapsed = 0ms
2025-12-06T20:27:55Z INFO Host authorized by MTA-STS policy (mta-sts.authorized) queueId = 278099417941147919, queueName = "remote", from = "[email protected]", to = ["[email protected]"], size = 1198, total = 1, domain = "gmail.com", hostname = "alt1.gmail-smtp-in.l.google.com", details = ["gmail-smtp-in.l.google.com", "*.gmail-smtp-in.l.google.com"], strict = true
2025-12-06T20:27:55Z INFO Error fetching TLSA record (dane.tlsa-record-fetch-error) queueId = 278099417941147919, queueName = "remote", from = "[email protected]", to = ["[email protected]"], size = 1198, total = 1, domain = "gmail.com", hostname = "alt1.gmail-smtp-in.l.google.com", causedBy = DNS error (mail-auth.dns-error) { details = "DNSSEC Negative Record Response for _25._tcp.alt1.gmail-smtp-in.l.google.com. IN TLSA, Bogus" }, strict = false, elapsed = 57ms
2025-12-06T20:36:55Z INFO Message rescheduled for delivery (queue.rescheduled) queueId = 278099417941147919, queueName = "remote", from = "[email protected]", to = ["[email protected]"], size = 1198, total = 1, nextRetry = 2025-12-06T22:36:55Z, nextDsn = 2025-12-08T22:44:09Z, expires = 2025-12-07T22:42:16Z
2025-12-06T20:36:55Z INFO Delivery attempt ended (delivery.attempt-end) queueId = 278099417941147919, queueName = "remote", from = "[email protected]", to = ["[email protected]"], size = 1198, total = 1, elapsed = 676181ms
2025-12-06T20:48:13Z INFO Invalid EHLO command (smtp.invalid-ehlo) listenerId = "smtp", localPort = 25, remoteIp = ipv4, remotePort = 54019, domain = "User"
2025-12-06T20:48:13Z INFO Authentication not allowed (smtp.auth-not-allowed) listenerId = "smtp", localPort = 25, remoteIp = ipv4, remotePort = 54019
2025-12-06T21:00:12Z INFO Banned due to scan (security.scan-ban) listenerId = "http", localPort = 8080, remoteIp = myipv4, remotePort = 55906, remoteIp = myipv4, path = "/.well-known/acme-challenge/file.php"
2025-12-06T21:00:12Z INFO Blocked IP address (security.ip-blocked) listenerId = "http", localPort = 8080, remoteIp = myipv4, remotePort = 55914

All required DNS records (including TLSAs) are updated, except an A record pointing to server and DNSSEC enabled.
For TLS connections, I'm using fullchain.pem and privkey.pem wildcard certificates, created with letsencrypt dns challenge.

[jeremiah]

Looks like you have network issues? The first line has at it's end:

causedBy = SMTP error occurred (smtp.error) { details = "I/O Error", reason = "Network is unreachable (os error 101)" },

[aoor9]

@jeremiah I don't understand this issue: if IMAP connection works then it should be the same for SMTP, since I exposed the machine and its relative ports, unless... the application is trying to use my v6 ip, but I can't make it public unlike the v4 one. If that's it, what about the errors below (EHLO, "Authentication not allowed" etc.)?

[jeremiah]

IMAP and SMTP are separate protocols, run by separate processes. They use different ports and may use different IP addresses as well. Just because IMAP (Internet Mail Access Protocol) works doesn't mean SMTP works (Simple Mail Transfer Protocol).

To understand more about why the SMTP error occurred, one would have to know more about your configuration and any firewalls on your device.