docs: credentials.md for git/mailbox creds, notify-creds, and SMTP ports

New docs/credentials.md covers member git-account provisioning, the
notify-creds backfill command (flags + behavior), required env, and the
two SMTP paths — transactional AGENTBBS_SMTP_* (STARTTLS :587) vs. the
gateway loopback relay AGENTBBS_MAIL_SMTP_ADDR (:25 into Mailu),
clarifying why :25 is correct and that 465 (not "467") is implicit-TLS.

Cross-linked from README ops and docs/mail.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -85,6 +85,10 @@ Ops:
 ./agentbbs notify-creds --user alice --mail --send
 ```
 
+Member git accounts, mailbox welcome emails, `notify-creds`, and the two SMTP
+paths (transactional `:587` vs. the gateway relay `:25`) are documented in
+[`docs/credentials.md`](docs/credentials.md).
+
 ## Deploy
 
 ### Hosting requirements

docs/credentials.md

@@ -0,0 +1,94 @@
+# Member credentials — git accounts, mailboxes & the `notify-creds` backfill
+
+Every **verified** AgentBBS member gets, for free:
+
+- a **git account** on `git.profullstack.com` (the self-hosted Forgejo backing
+  AgentGit) — BBS membership *is* the git account, and
+- a **mailbox** at `<name>@mail.profullstack.com` (self-hosted Mailu — see
+  [`mail.md`](mail.md)).
+
+This doc covers how those credentials are delivered by email, and the
+`agentbbs notify-creds` ops command that (re)sends them.
+
+## Git accounts (automatic)
+
+When a member confirms their email, `provisionGit` (`cmd/agentbbs/main.go`):
+
+1. **Creates** their Forgejo account (`forgejo.EnsureUser`) with a generated
+   one-time password (`must_change_password`), if it doesn't exist.
+2. **Registers** the SSH key they signed in with (`forgejo.EnsureKey`) so they
+   push with the same key — no git password.
+3. **Emails** them the web sign-in link, username, and the one-time password
+   (`gitWelcomeEmailBody`) via the transactional SMTP relay.
+
+It's idempotent and best-effort: failures are logged, never blocking BBS
+verification, and it's a no-op when Forgejo is unconfigured. It runs on email
+verification (`join@` and the web `/verify` link) and again, asynchronously, on
+each BBS login so an existing member's key is kept in sync.
+
+## `notify-creds` — backfill / re-send (ops)
+
+The git- and mailbox-credential emails were added after some accounts already
+existed, so `notify-creds` lets the operator send them to members who never
+received them. Run it on the host where the DB and env live.
+
+```bash
+agentbbs notify-creds                 # PREVIEW for all verified members (sends nothing)
+agentbbs notify-creds --send          # really send git + mailbox to everyone verified
+agentbbs notify-creds --git --send    # git creds only
+agentbbs notify-creds --mail --send   # mailbox creds only
+agentbbs notify-creds --user alice,bob --send
+```
+
+| Flag | Effect |
+|---|---|
+| *(none)* | **Preview only** — scans and prints intended actions; resets no passwords, sends no mail. |
+| `--send` | Actually reset passwords, ensure aliases, and send email. |
+| `--git` | Include git creds (default: both when neither `--git`/`--mail` is given). |
+| `--mail` | Include mailbox creds. |
+| `--user a,b` | Restrict to a comma-separated allow-list (default: all verified). |
+| `--limit N` | Max accounts to scan (default 100000). |
+
+What `--send` does per verified member (banned / unverified / no-email are
+skipped):
+
+- **git** — `forgejo.EnsureUserReset`: creates the account if missing, otherwise
+  **resets it to a fresh one-time password** (the original is not recoverable),
+  then emails the login link + username + password. The reset clobbers any
+  password a member set themselves, which is why it only runs under `--send`.
+- **mail** — `forwardemail.CreateAlias` to ensure the `<name>@<domain>` alias,
+  then emails the address + webmail link.
+
+Safety rails: it **refuses `--send` when SMTP is unconfigured**, and
+**warns-and-skips** the git or mail channel when Forgejo / forwardemail are
+unconfigured. It prints a per-channel `sent / failed` summary and exits non-zero
+on any failure.
+
+> The `--mail` path uses the **forwardemail.net** alias API
+> (`AGENTBBS_FORWARDEMAIL_*`), which is independent of the self-hosted Mailu
+> mailbox stack in [`mail.md`](mail.md). Use whichever your deployment has wired.
+
+## Required env
+
+| Var | Default | For |
+|---|---|---|
+| `AGENTBBS_FORGEJO_URL` | unset | git — Forgejo base URL, e.g. `https://git.profullstack.com` |
+| `AGENTBBS_FORGEJO_ADMIN_TOKEN` | unset | git — Forgejo admin token (create/reset users + keys) |
+| `AGENTBBS_FORWARDEMAIL_API_KEY` | unset | mail — forwardemail.net API key |
+| `AGENTBBS_FORWARDEMAIL_DOMAIN` | `AGENTBBS_MAIL_DOMAIN` | mail — alias domain (falls back to the mail domain, default `mail.profullstack.com`) |
+| `AGENTBBS_WEBMAIL_URL` | unset | mail — webmail link put in the email (optional) |
+| `AGENTBBS_SMTP_HOST` / `_FROM` | unset | **sending** all of the above emails (required to actually send) |
+| `AGENTBBS_SMTP_PORT` / `_USER` / `_PASS` | `587` / unset / unset | SMTP submission (STARTTLS) |
+
+## Two SMTP paths (and why one is `:25`)
+
+AgentBBS has **two different SMTP configs** — don't confuse them:
+
+| Config | Default | Role |
+|---|---|---|
+| `AGENTBBS_SMTP_*` (`internal/mail`) | port **`587`** (STARTTLS) | **Transactional sender** — `join@` confirmation codes and all `notify-creds` emails. This is an authenticated *submission* port. **Implicit-TLS `465` is not supported** by this code path (it negotiates STARTTLS); use 587 or another STARTTLS port. |
+| `AGENTBBS_MAIL_SMTP_ADDR` (`internal/mailbox`) | **`127.0.0.1:25`** | **Gateway relay** — how the in-BBS `Mail` client injects members' outbound mail into the **on-box Mailu/Postfix MTA**. `:25` is correct here: it's a trusted *loopback* hand-off to the local MTA, not a remote authenticated client. 465/587 are submission ports for *remote* clients and don't apply. |
+
+So a `127.0.0.1:25` in the mail config is intentional, not a bug. (And there is
+no SMTP port `467` — the implicit-TLS submission port is `465`.) See
+[`mail.md`](mail.md) for the full Mailu stack.

docs/mail.md

@@ -103,6 +103,13 @@ Without `AGENTBBS_MAIL_API_TOKEN` auto-provisioning is skipped (the address is
 still shown); without `AGENTBBS_MAIL_MASTER_PASS` the gateway can't open
 mailboxes.
 
+> **`AGENTBBS_MAIL_SMTP_ADDR` is `127.0.0.1:25` on purpose** — it's the gateway's
+> *loopback* hand-off into the on-box Mailu/Postfix MTA, not a remote submission
+> client, so `25` is correct (465/587 are for authenticated remote clients).
+> This is a separate config from `AGENTBBS_SMTP_*` (the transactional sender for
+> confirmation codes and `notify-creds`, which defaults to STARTTLS `:587`). See
+> [`credentials.md`](credentials.md#two-smtp-paths-and-why-one-is-25).
+
 ### Why the gateway talks to Dovecot directly (plaintext loopback)
 
 Mailu's **front** (nginx mail proxy) pre-authenticates every IMAP/SMTP login