How to OTP / one-time-code emails

Here is how to OTP / one-time-code emails reliably — so they reach the inbox, every time.

The essentials

One-time-code email must arrive instantly and reliably. Use a dedicated transactional stream, authenticate fully, and track delivery events so failed codes trigger a fallback.

Deliverability checklist

• Authenticate the sending domain with SPF, DKIM and DMARC.
• Send from a dedicated, reputation-clean IP.
• Track delivery, bounces and complaints and act on them.

How Rainmail helps

Rainmail sends from your own domain on a dedicated, isolated IP with SPF, DKIM, DMARC, reverse-DNS and managed warm-up handled for you, plus an AI that watches your list health and deliverability. It also welcomes the senders Amazon SES, SendGrid and Mailchimp reject — from $8, cheaper per email than SES. Run the free 10-second checker or see plans.