Editing Training 2022 Linux team/ (section)

==Training session on Basic qmail training 24 March 2023 - Tetra Support Staff - Biswajit Banerjee==

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'''Video summary:''' "Basic qmail training" -- a clear English-language session explicitly scoped as diagnosis/troubleshooting knowledge, not qmail installation (Tetra doesn't build new qmail environments, but still supports the few legacy ones that exist, plus Kloxo's internal use of qmail). Demonstrates identifying a running qmail environment via `netstat -ntplu` (spotting MySQL, ClamAV, a separate spam-scanning engine, POP3, and port 25/SMTP via `tcpserver` -- notably no IMAP on this particular primitive setup) and `qmailctl stat` to confirm all qmail sub-services are up. Covers the SMTP relay/control-file configuration for outbound mail: a client (HACO India) is shown routing all outbound mail through `server-relay.tetrain.com` via qmail's `smtproutes` control file, where a blank/no-domain entry acts as a catch-all default relay; explains how to safely change which relay server a domain uses (first confirm the new relay server's IP is allow-listed on the target relay, then update the control file) and explicitly warns against changing it reflexively on a single complaint -- if mail were truly going to spam/junk for everyone using that relay, many customers would be reporting it, so an isolated complaint usually means something specific to that one customer, not the shared relay. Walks through qmail's multi-log tracing pattern in detail, paralleling the Zimbra/Postfix tracing training elsewhere on this wiki: SMTP-level connections land in `/var/log/qmail/qmail-smtpd/current` (piped through `tai64nlocal` to get human-readable timestamps); antivirus/spam scanning results appear in the mail log (ClamAV plus the separate spam engine, tagged with spam-score info); and actual delivery status is tracked separately in `qmail-send`'s log, where entries are tagged "local" (delivered to a local/virtual-domain mailbox) or "remote" (relayed onward, typically via the configured relay server's IP) with numeric delivery/message IDs and explicit "delivered"/"bounced" (symbol-marked) outcomes -- e.g. a bounce caused by "no such mailbox." Clarifies virtual-domain handling: a domain not present locally as a virtual domain gets routed remotely rather than delivered locally. Ends with a brief live Q&A confirming the local/remote distinction, before the session is interrupted by an unrelated incoming maintenance-window request for a database downtime window.