docs(manual): document --from on account edit and the send-as address

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

USER-MANUAL.md

@@ -261,9 +261,15 @@ emcli account edit --name work --mode RW --smtp-host smtp.example.com --smtp-por
 emcli account edit --name gmail --password 'new-app-password'   # rotate the app password
 ```
 
-> Note: the flag form of `account edit` covers connection/auth fields and `--subject-regex`. To
+```bash
-> toggle whitelists or `process-backlog`, use the interactive form (`emcli account edit --name X`
+emcli account edit --name work --from 'Work Team <you@yourdomain.com>'   # set the send-as address
-> with no other flags), or the `whitelist` commands in section 6.
+emcli account edit --name work --from ''                                 # clear it (revert to username)
+```
+
+> Note: the flag form of `account edit` covers connection/auth fields, `--from`, and
+> `--subject-regex`. Passing `--from ''` clears the send-as address so mail falls back to the login
+> username. To toggle whitelists or `process-backlog`, use the interactive form (`emcli account edit
+> --name X` with no other flags), or the `whitelist` commands in section 6.
 
 **Remove an account** (requires `--yes`):
 
@@ -421,6 +427,11 @@ emcli send --account gmail --to a@x.com --subject "Re: Hi" --body "thanks" \
 client. The source is subject to the inbound whitelist — you can't reply to mail you aren't allowed
 to see.
 
+The message's `From:` is the account's send-as address (`--from`, set on `account add`/`edit`); if
+none is configured it falls back to the login username. A display-name address like
+`Steve Cliff <me@example.com>` shows the name in the recipient's client while the bare address is
+used for the SMTP envelope.
+
 ---
 
 ## 8. The JSON envelope