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Fix iRedMail by identifying which path is broken—Internet delivery in, authenticated submission out, or mailbox retrieval—and then matching the exact log error to that path. Start with one controlled test in each direction, correlate its timestamp and queue ID in Postfix and Dovecot logs, verify that the required services and ports are listening, and only then change DNS, firewall, TLS, or filtering settings.
Start by classifying the failure
“Email is not working” can describe three different systems. Incoming Internet mail reaches Postfix on SMTP port 25, passes through the filtering and local-delivery chain, and is written to a mailbox. Outgoing mail from a user reaches Postfix submission on port 587 (or 465 when enabled), is queued, and is delivered to a remote server. IMAP or POP3 then lets a mail client retrieve the message. A failure in one path does not prove that the others are broken.
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| What you observe | Most relevant layer | First evidence to collect |
|---|---|---|
| External senders receive a timeout or connection refusal | DNS, firewall, NAT, security group, or port 25 listener | MX and A lookups, port-25 connectivity, Postfix listener state |
| Postfix accepts an outgoing message but it remains deferred | Destination DNS, network connection, TLS, policy, or recipient response | The queue ID, all lines for that ID, and the remote SMTP reply |
| SMTP submission works but no message appears in a mailbox | Amavisd, LMTP, Dovecot, or mailbox path | Postfix, Amavisd, and Dovecot lines at the delivery timestamp |
| A user cannot send from a mail application | Submission port, username, password, or TLS mode | The client settings and Dovecot/Postfix authentication error |
| Webmail login works but a desktop client cannot retrieve mail | IMAP/POP listener, certificate, or client protocol settings | Dovecot log entry and the client’s selected port and encryption |
Use the failure direction to choose a reversible fix first. Correcting a client port or a DNS record is safer than changing Postfix or Dovecot policy. Do not infer a cause from a client popup or from status=deferred alone.
Capture evidence before changing configuration
Reproduce the problem with a single, identifiable message. Send one test from an external account to an iRedMail mailbox, and one from that mailbox to an external account. Record the sender, recipient, exact UTC or local time, and subject. Those details let you correlate the event across services.
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- Watch the primary Ubuntu mail log while repeating the test. Run
sudo tail -F /var/log/mail.log. Keep the output from the moment the SMTP connection starts through final delivery, rejection, or deferral. - Check warning and error logs for the same timestamp. Use
sudo tail -F /var/log/mail.warn /var/log/mail.err. A warning in one file may explain a terse line inmail.log. - Inspect Dovecot’s per-service logs. iRedMail documents Dovecot logs under
/var/log/dovecot/*.log. Search the relevant file for the username, mailbox, and timestamp. - Save the queue ID. Postfix assigns an ID to accepted mail. Search every related line with that ID; the first acceptance line, transport attempt, filtering hand-off, and final status form one story.
- Capture the exact SMTP, LMTP, or IMAP text. “Deferred” is only an outcome. The preceding destination response or local-delivery error identifies the actionable cause.
If you temporarily increase Postfix logging to diagnose a difficult case, restore the normal level afterward. Ubuntu’s Postfix guidance warns that verbose logging becomes very noisy and can obscure the useful events.
Verify services and listening ports
Before changing mail settings, confirm that the components are running. Check Postfix, Dovecot, Amavisd, and the webmail stack with systemd; service names can vary for the web server, so use the name installed on your host.
sudo systemctl status postfix dovecot amavis
sudo systemctl --failed
sudo ss -ltnpCompare the listeners with the role each port must perform:
| Port | Service and purpose | What a missing or blocked port means |
|---|---|---|
| 25/TCP | Postfix SMTP for server-to-server delivery | Other mail servers cannot deliver Internet mail to your domain. Port 25 must be reachable for inbound mail. |
| 587/TCP | Postfix authenticated submission for end users | Mail applications cannot submit outgoing mail using the normal client path. |
| 465/TCP | Postfix submission over implicit SSL, when enabled | Clients configured for 465 fail unless that listener and mode are enabled. |
| 143/TCP, 993/TCP | Dovecot IMAP with STARTTLS on 143 or SSL on 993 | Clients cannot browse synchronized mailboxes. |
| 110/TCP, 995/TCP | Dovecot POP3 with STARTTLS on 110 or SSL on 995 | POP clients cannot download mail. |
| 24/TCP | LMTP, normally loopback-only, for local delivery | A local hand-off can fail even while public SMTP accepts the message. |
A process listening only on 127.0.0.1 is intentionally local. That is expected for LMTP; it is not sufficient for port 25, which must be reachable from other mail servers. If a cloud security group, host firewall, router, or NAT device blocks a required public port, a local service restart will not solve the problem.
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Fix mail that cannot arrive from the Internet
Confirm MX and A records
An MX record tells remote senders which host accepts mail for your domain. The MX target must resolve to an A record (or an appropriate IPv6 record), and that host must resolve to the server that actually listens on port 25. Query both the domain and its mail host from a network outside your server:
dig +short MX example.com
dig +short A mail.example.com
dig +short AAAA mail.example.comReplace the example names with your real domain and MX host. If MX points to an old provider, an internal-only name, or a host whose address is not your iRedMail server, remote mail is going somewhere else. DNS changes also depend on the records’ TTL; allow caches to expire before judging a correction.
Test port 25 from outside
Use a machine on another network to test the advertised MX host, not merely localhost on the mail server. A timeout usually indicates a firewall, security-group, NAT, routing, or upstream provider restriction. A connection refusal usually means the host is reachable but no Postfix listener accepts the connection, or a firewall is actively rejecting it. After correcting the network path, confirm the SMTP banner in /var/log/mail.log.
Check the server identity and reverse DNS
Set the server’s fully qualified domain name (FQDN) consistently in the operating system and Postfix. The FQDN must resolve forward, and its reverse PTR record should resolve back to the same name. Reverse DNS is not listed as a mandatory iRedMail record, but it is highly recommended for a credible sending identity.
Postfix can reject a peer with an error such as Helo command rejected: Host not found when the domain presented in HELO/EHLO has no A record. Ensure the HELO name has a valid public address before investigating mailbox credentials.
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Fix outgoing mail that is accepted but deferred
Find the queue ID in /var/log/mail.log, then read the destination attempt and every preceding line for that ID. The remote server’s response is more useful than the word deferred.
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|---|---|---|
| DNS lookup failure or “Host not found” | Broken destination DNS, local resolver failure, or invalid HELO identity | Query the recipient domain’s MX/A records and verify the server FQDN. |
| Connection timed out | Remote firewall, routing problem, blocked outbound SMTP, or unreachable host | Test DNS and TCP connectivity; check provider egress restrictions. |
| Connection refused | Remote SMTP service is unavailable or rejecting the network path | Retry later and inspect the complete remote response. |
| TLS negotiation or certificate error | Protocol, certificate, or remote TLS compatibility problem | Read the TLS lines and verify system time, certificates, and the negotiated mode. |
| Relay denied or policy rejection | Unauthenticated submission, recipient policy, reputation, or sender authorization | Confirm the user submitted through port 587/465 and review the exact SMTP code. |
| Recipient rejected after connection | Address, domain, or recipient policy problem | Correct the address or follow the remote server’s stated requirement; do not repeatedly resend blindly. |
Do not delete the queue simply because a message is deferred. Preserve the queue ID and response while diagnosing. Once the underlying problem is fixed, Postfix can retry according to its normal schedule; a controlled retry can confirm the correction.
Correct DNS records that affect delivery and reputation
For every hosted domain, iRedMail’s DNS guidance requires A and MX records. The following records are optional in the strict sense but strongly recommended:
- PTR (reverse DNS): maps the sending IP back to the server’s FQDN. Request it from the IP address provider.
- SPF: publishes which hosts are authorized to send for the domain.
- DKIM: signs outgoing messages so recipients can verify that the message was authorized and not altered.
- DMARC: tells receiving systems how to evaluate SPF/DKIM alignment and where to report failures.
These records improve identity and deliverability, but they do not make a closed port 25 reachable or repair a stopped Postfix service. Validate each record at the public DNS provider and check that the name in Postfix’s HELO command has a matching A record.
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Use the correct client settings
Enter the complete email address as the username, not only the part before the at-sign. Select the encryption mode that matches the port; choosing STARTTLS on an implicit-SSL port (or the reverse) causes an apparent connection or authentication failure.
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|---|---|---|---|
| Send mail (recommended submission) | 587 | STARTTLS | Required; use the full email address |
| Send mail (implicit SSL, if enabled) | 465 | SSL/TLS from connection start | Required; use the full email address |
| Read mail with IMAP | 143 | STARTTLS | Required |
| Read mail with IMAP | 993 | SSL/TLS from connection start | Required |
| Read mail with POP3 | 110 | STARTTLS | Required |
| Read mail with POP3 | 995 | SSL/TLS from connection start | Required |
IMAP and POP retrieve mail; they do not replace SMTP submission. If Dovecot logs Plaintext authentication not allowed without SSL/TLS, enable STARTTLS or SSL/TLS in the client. Do not weaken Dovecot to permit passwords over an unencrypted connection.
Repair filtering and local delivery
Recognize an Amavisd hand-off failure
iRedMail commonly sends mail from Postfix to Amavisd for spam and virus scanning before local delivery. A Postfix error connecting to 127.0.0.1:10024 means Amavisd is not accepting the hand-off. On Ubuntu or Debian, restart the service and immediately inspect its logs:
sudo systemctl restart amavis
sudo systemctl status amavis
sudo journalctl -u amavis --since "15 minutes ago"If Amavisd repeatedly stops, check its resource and dependency errors rather than repeatedly restarting it. The iRedMail project states that a low-traffic production server with spam and virus scanning enabled requires 4 GB of memory; the project page does not state a publication year for that figure. Systems below that level may fail to keep Amavisd or ClamAV running reliably.
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Trace LMTP and Dovecot delivery
If Postfix accepts a message and filtering completes but the mailbox remains empty, follow the local hand-off. LMTP normally listens on loopback port 24. Look for an LMTP delivery response in mail.log, then match the recipient and timestamp in /var/log/dovecot/*.log. Authentication can succeed while delivery still fails because of a mailbox path, quota, permissions, namespace, or Dovecot service error.
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Do not “fix” a missing message by changing the client first. Confirm whether Dovecot received the message and which mailbox it selected. If local delivery reports success but the user sees nothing, verify that the client is connected to the same account and folder namespace and that it has refreshed or subscribed to the expected folder.
Separate webmail success from SMTP and IMAP health
Webmail is only one client of the stack. A successful webmail login proves that the web application can reach its configured backend; it does not prove that public SMTP port 25 is reachable, that submission on 587 works, or that a desktop client can negotiate IMAP TLS. Conversely, a working IMAP connection does not prove that outgoing SMTP is authenticated.
Test each interface independently: an external SMTP delivery to test inbound mail, an authenticated submission test for outbound mail, and an IMAP or POP login for retrieval. Record which test fails and use only that path’s logs while troubleshooting.
Prepare a useful support request when local checks do not resolve it
When the evidence points to an iRedMail-specific configuration or an unfamiliar error, provide a reproducible, sanitized bundle to the iRedMail support forum or its paid professional support service. Remove passwords, private keys, message bodies, and personal addresses while preserving domain structure and error text.
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- The affected direction: inbound, outbound, or mailbox access.
- Ubuntu release and iRedMail version.
- Local time zone and exact timestamps for one failed test.
- Postfix queue ID and all related lines from
/var/log/mail.log, plus relevantmail.warnandmail.errlines. - Relevant Dovecot and Amavisd log lines.
- The complete SMTP, LMTP, or IMAP response, including numeric codes.
- Public DNS results for A, MX, and (when configured) PTR, SPF, DKIM, and DMARC.
- Listening-port output and confirmation of firewall, security-group, or NAT rules.
This bundle lets support distinguish a network reachability issue from a queue, filtering, authentication, or local-delivery fault without asking you to repeat the same tests.
Quick Recap
A repeatable recovery checklist
- Send one controlled test in each direction and note timestamps, recipients, and queue IDs.
- Watch
/var/log/mail.log,/var/log/mail.warn,/var/log/mail.err, and the applicable Dovecot log while reproducing the failure. - Classify the failure as inbound SMTP, outbound submission/transport, or mailbox retrieval/local delivery.
- Confirm Postfix, Dovecot, Amavisd, and webmail services are running; inspect listeners with
ss -ltnp. - For inbound problems, verify MX/A records, public port 25, firewall/NAT rules, PTR, and the Postfix HELO name.
- For deferred outbound mail, use the destination’s exact response to choose a DNS, network, TLS, policy, or recipient fix.
- For client errors, use the full email address and pair each port with the correct STARTTLS or SSL mode.
- For missing local mail, follow the Amavisd hand-off, LMTP response, and Dovecot mailbox logs; investigate resource pressure if Amavisd or ClamAV stops.
- Restore normal logging, retry once after the correction, and document the result with the original evidence.
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