How do I make sure login codes get delivered fast?

To get login codes delivered as fast as possible, focus on the bottleneck: the channel, your email/SMS setup, and the destination service’s reputation.

If you mean email codes

• Use a strong email provider: Send through a reputable service like SendGrid, Amazon SES, Mailgun, or Postmark.
• Set up authentication correctly:
  • SPF
  • DKIM
  • DMARC This helps inbox providers trust your messages and reduces delay/spam filtering.
• Use a dedicated sending domain or subdomain for codes, e.g. auth.yourdomain.com.
• Keep the content simple: plain, short emails with a clear code and no heavy images, links, or attachments.
• Avoid spam triggers: too many links, urgent/marketing language, or inconsistent sender names can slow delivery.
• Warm up your domain/IP if you’re sending from a new domain or IP.
• Monitor delivery with logs, bounces, and spam complaints.

If you mean SMS codes

• Use a reliable SMS gateway: Twilio, Vonage, Sinch, MessageBird, etc.
• Choose local/approved sender routes in each country; SMS rules vary by region.
• Keep the message short so it fits in one segment and is less likely to be delayed.
• Avoid sending in bursts from a new number or route; carriers may throttle.
• Use a fallback provider if one route is slow or failing.
• Track delivery receipts and carrier errors.

Improve the user experience

• Show “Resend code” after a short delay with rate limits.
• Offer backup methods: authenticator app, backup codes, passkeys, or push approval.
• Detect autofill for OTP input on mobile to reduce time-to-login.
• Measure delivery time by provider, region, and time of day.

Best overall approach

If speed matters a lot, don’t rely on only email or SMS:

• Prefer passkeys or authenticator apps for instant login
• Use push notifications or TOTP as alternatives
• Keep email/SMS as fallback

If you tell me whether you mean email, SMS, or both, I can give you a more specific checklist.