You are helping me build the following AI agent workflow.

## Goal
Multi-Factor Authentication via Voice and Email: On form submission, it calls the user with a spoken code via ClickSend, then emails a second code via SMTP for two-step verification.

## Specification
- What it does: Get verified instantly when you submit a form by receiving a spoken code on your phone followed immediately by a second code in your email. This two-step process ensures your account stays secure while letting you complete your submission quickly.
- Trigger: Triggered by an event (Event · on form submission)
- Autonomy: Fully hands-off
- Expected setup effort: about an afternoon
- Tools/services involved:
  - ClickSend API: Sending voice calls with verification codes
  - SMTP: Sending email verification codes
  - Code: Formatting verification code for voice clarity

## Known pitfalls, handle each one explicitly in your implementation
1. ClickSend calls may fail if the phone number format is invalid so always validate E.164 formatting before sending.
2. SMTP servers often block automated emails from unknown IPs so configure SPF and DKIM records to improve deliverability.
3. Voice recognition errors can cause verification failures so implement a retry mechanism with a limited number of attempts.
4. Code expiration times must be strictly enforced in the validation logic so users cannot reuse old codes after the window closes.

## Reference implementation
https://n8n.io/workflows/3142 (workflow template)
Fetch and inspect this before building. If it matches my stack, adapt it;
if not, rebuild the pattern with my tools.

## Process requirements
1. Before building: ask me which of the listed tools I actually use and
   what my platform is (n8n / Make / code / other). Do not assume.
2. Adapt the pattern to my answers; do not force the reference stack.
3. Address every pitfall above; tell me how you handled each.
4. Provide a test plan I can run before letting this touch real data.
5. Ask before any step that sends messages, modifies data, or spends money.

Source: https://usecasesforagents.com/use-case/multi-factor-authentication-via-voice-and-email/ via usecasesforagents.com