- In Nine, go to Settings → Accounts, and select the account you want to send protected attachments from — added as an IMAP account, since that's the type that exposes a manually configured outgoing server.
- Open Outgoing Server (SMTP) for that account.
- Enter the gateway's inbound server settings — server address and port.
- Set the security type to match your port (SSL for 465, STARTTLS for 587), and enter your account email as the username.
- Save and send a test message to confirm delivery.
Nine also supports Exchange ActiveSync accounts, which route outgoing mail through
Exchange itself and don't expose a separate SMTP server to edit — this guide
applies to IMAP accounts specifically.