docs: design for send-as From address field

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-23 20:06:38 +01:00
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+# Send-as "From" address — design
+
+**Date:** 2026-06-23
+**Status:** Approved (pending spec review)
+
+## Problem
+
+An account's configuration has no field for the email address used as the
+`From:` when sending mail. Today the From is silently aliased to the login
+username (`internal/cli/send.go:26`, `From: acc.Username`), and neither
+`store.Account` nor the `accounts` table has any `from`/`address`/`email`
+column.
+
+This works only when the login username is exactly the desired send-as
+address. It breaks for:
+
+- providers where the login is an account ID rather than an email,
+- sending from an **alias** of the mailbox,
+- wanting a **display name** (`Steve Cliff <me@…>`) rather than a bare address,
+- Gmail App Passwords where envelope-from and header-from may differ.
+
+## Decisions
+
+- **Field shape:** a single freeform RFC 5322 From identity — bare
+  (`me@stevecliff.com`) or with a display name
+  (`Steve Cliff <me@stevecliff.com>`). One field, not a split
+  address/display-name pair.
+- **Fallback:** when the from-address is blank, fall back to
+  `Account.Username` (current behaviour). No migration/backfill of existing
+  accounts required; they keep working unchanged.
+
+## Design
+
+### 1. Data model
+
+Add `FromAddress string` to `store.Account` and a `from_address TEXT` column to
+the `accounts` table. **Not encrypted** — it is not a secret (it appears in
+every outgoing header), so it is stored as plaintext like `username`.
+
+### 2. Fallback in one place
+
+Add a method so the fallback rule lives in exactly one spot:
+
+```go
+// SendFrom returns the From identity for outgoing mail, falling back to the
+// login username when no explicit from-address is configured.
+func (a Account) SendFrom() string {
+	if a.FromAddress != "" {
+		return a.FromAddress
+	}
+	return a.Username
+}
+```
+
+`internal/cli/send.go` changes `From: acc.Username` → `From: acc.SendFrom()`.
+
+### 3. Envelope sender vs header From
+
+A display-name From breaks the SMTP envelope: `c.SendMail("Steve <me@…>", …)`
+is invalid — the envelope sender must be the **bare** address.
+
+- `mail.BuildMIME` keeps using the full `m.From` for the `From:` header
+  (go-message renders `Name <addr>` correctly via `SetAddressList`).
+- `mail.SendSMTP` derives the envelope sender as the bare address:
+  `gomail.ParseAddress(m.From).Address`. If parsing fails, fall back to the raw
+  `m.From` (preserves today's behaviour for plain addresses).
+
+Header carries the display name; envelope carries the bare address.
+
+### 4. Migration
+
+The schema is v1, applied via `CREATE TABLE … IF NOT EXISTS`, which will not add
+a column to an existing DB, and there is no migration runner yet.
+
+- Add the `from_address` column to the `CREATE TABLE accounts` statement (new
+  DBs get it directly).
+- In `store.Open`, after applying the schema, run a version-gated migration: if
+  the stored `schema_version` is `< 2`, execute
+  `ALTER TABLE accounts ADD COLUMN from_address TEXT` and set `schema_version`
+  to `2`.
+- Bump the `schemaVersion` constant to `2`.
+
+SQLite `ALTER TABLE … ADD COLUMN` is cheap and safe. The migration is
+idempotent under the version gate.
+
+### 5. Inputs & validation
+
+- **CLI:** add a `--from` flag to `account add` and `account edit`. On `edit`,
+  follow the existing `fs.Visit` overlay pattern (only set when the flag was
+  passed).
+- **TUI:** add a `FromAddress` field to `tui.Fields`, a `fieldDef`
+  (`{key: "from_address", label: "From address (optional)"}`), and wire it
+  through `ToAccount`, `FieldsFromAccount`, `fieldValue`, and `collect`.
+- **Validation:** when the from-address is non-empty, reject it unless
+  `gomail.ParseAddress` accepts it (covers bare and display-name forms). A
+  blank from-address is always valid (→ fallback). Applied in
+  `Fields.Validate` and on the `account add`/`edit` flag path.
+- **Persistence:** thread `from_address` through `AddAccount`, `UpdateAccount`,
+  `scanAccount`, and the three `SELECT` column lists in
+  `internal/store/account.go`. Stored via `nullStr` (blank → NULL).
+
+### 6. Tests
+
+- `SendFrom()`: returns the from-address when set; returns username when blank.
+- `SendSMTP` envelope: when From is `Name <addr>`, the envelope sender passed to
+  the server is the bare `addr` (table test on the extraction helper).
+- Migration: open a v1 DB with no `from_address` column → column is added,
+  `schema_version` becomes 2, and an existing account still sends from its
+  username.
+- `Fields.Validate`: rejects a malformed from-address; accepts bare and
+  display-name forms; accepts blank.
+- Round-trip: `FieldsFromAccount` then `ToAccount` preserves `FromAddress`.
+
+## Out of scope (YAGNI)
+
+- Separate envelope-from override field (derive it from From instead).
+- Per-message From override at send time.
+- Multiple aliases per account.