How to Use Email OTP Two-Factor Authentication in WordPress

What Is the Email OTP 2FA feature?

Email OTP 2FA uses the user’s email address as the second factor. After entering the password, the user receives a 6-digit code via email and must enter it to complete the login.

This is a fallback for users who don’t want to use an authenticator app, or for sites where email is the most reliable channel.

Why You Need It

TOTP 2FA requires an authenticator app, which has barriers:

• No smartphone: Some users don’t have a smartphone
• App installation friction: Users don’t want to install yet another app
• Lost device: If the user loses their phone, they’re locked out
• Email is universal: Almost everyone has email and can receive codes

Email OTP 2FA is a good middle ground: better than password-only, more accessible than TOTP.

Trade-offs vs TOTP

Email OTP is less secure than TOTP because:

• Email interception: If the user’s email is compromised, the attacker can get the OTP
• Email delays: Email delivery can be slow (1-5 minutes), causing login friction
• Phishing: Sophisticated phishing kits can intercept emails in real-time

For high-security sites, prefer TOTP. For accessibility, use Email OTP.

How to Use Email OTP 2FA in WordPress

Step 1: Configure SMTP

Before enabling Email OTP 2FA, configure SMTP Settings to ensure reliable email delivery. 2FA codes that don’t arrive lock users out.

Step 2: Navigate to Settings

Click into the Classic Monks plugin settings in your WordPress dashboard.

Step 3: Go to the Security Tab

Click on the Security menu, then click the Two-Factor Auth subtab.

Step 4: Enable Email OTP

Scroll to Enable Email OTP and toggle on.

Step 5: Save Changes

Click Save Changes.

Step 6: Enable Email OTP for Your Account

Go to Users > Profile. In the “Two-Factor Authentication” section, enable Email OTP. Click “Send Test Code” to verify it works.

Step 7: Test

Log out. Log in with your username and password. After the password is verified, a 6-digit code is sent to your email. Enter the code to complete the login.

Configuration Options

Option	Description	Default
Enable Email OTP	Master toggle.	Off

Each user enables Email OTP individually from their profile. Admins can require it for specific roles from the plugin settings under Security > 2FA.

What Gets Affected

• The login flow: after password, a 6-digit code is sent via email
• The user profile: each user can enable Email OTP
• The WordPress admin: requires 2FA for users with Email OTP enabled
• The email deliverability: must be reliable (use SMTP)

What Does NOT Get Affected

• The user experience: only 1 extra click per login (after the code is received)
• The TOTP 2FA: still works independently
• The frontend: not affected
• The application passwords: separate authentication method

Advanced Options (Developers)

This feature registers 3 WordPress hooks in 2fa/two-factor-auth.php:

Actions:

• wp_ajax_nopriv_cm_resend_2fa_email calls cm_resend_2fa_email() (AJAX handler for resending OTP email)

Filters:

• authenticate calls CM_Two_Factor_Auth::authenticate() (Intercepts authentication for email OTP flow (priority 99))
• cm_2fa_rate_limit_enabled calls apply_filters() (Customizable filter)

// Hooked in 2fa/two-factor-auth.php
add_filter( 'authenticate', 'CM_Two_Factor_Auth::authenticate' );

The feature modifies WordPress behavior by registering or removing hooks. Disabling it reverses those changes and WordPress returns to its default behavior.

Troubleshooting

The OTP code is not being sent

Cause: Email deliverability issue or the toggle is off.
Fix: Verify the toggle is on. Test email delivery (use a plugin like Check Email). Configure SMTP Settings to use a reliable email service (Gmail SMTP, SendGrid, Mailgun, etc.).

The OTP code is rejected

Cause: The code has expired (default: 10 minutes).
Fix: Request a new code. If the issue persists, check the server’s time sync (the OTP is time-based).

The user is locked out of their account

Cause: The user can’t access their email.
Fix: An admin can disable Email OTP for the user from the user profile page. Or the user can use the recovery code (if TOTP is also enabled).

The OTP code arrives slowly

Cause: Email delivery delay (especially with shared hosting).
Fix: Use a reliable SMTP service (Gmail SMTP, SendGrid, etc.). Increase the OTP expiration time in the plugin settings under Security > 2FA.

I want to require Email OTP for specific user roles

Cause: Email OTP is opt-in by default.
Fix: Require 2FA (TOTP or Email OTP) for specific user roles from the plugin settings under Security > 2FA. Users in those roles will be forced to enable one of the 2FA methods.