The following code requires @gmail.com as an email domain for user registrations. You can change @gmail.com to any provider you want. The code below requires a user email to be collected during registration.

Validate the email address by domain on registration.php

<?php

/**
 * This example shows how to validate the email address by domain on registration.
 * The code below requires a user email to be collected during registration.
 *
 * Change the array $allowed_email_domains - add or remove what you need.
 * Add this code snippet to the end of the file functions.php in the active theme directory.
 *
 * Ultimate Member documentation: https://docs.ultimatemember.com/
 * Ultimate Member support (for customers): https://ultimatemember.com/support/ticket/
 */

/**
 * Custom validation for the field "E-mail Address" by domain on registration.
 * @author  Ultimate Member support <support@ultimatemember.com>
 * @param   array  $args
 */
function um_validate_email_domain( $args ) {

	// Change allowed email domains here
	$allowed_email_domains = apply_filters( 'um_allowed_email_domains', array(
			'gmail.com',
			'yahoo.com',
			'hotmail.com'
			) );

	// Change error message here
	$message = __( 'You can not use this email domain for registration', 'ultimate-member' );

	if ( isset( $args['user_email'] ) && is_email( $args['user_email'] ) ) {
		$email_domain = array_pop( explode( '@', trim( $args['user_email'] ) ) );
		if ( !in_array( $email_domain, $allowed_email_domains ) ) {
			UM()->form()->add_error( 'user_email', $message );
		}
	}
}
add_action( 'um_submit_form_errors_hook__registration', 'um_validate_email_domain', 20 );

Hi there,

Please advise on the code modifications to allowing whitelisting 2 domains instead of the above cod which is one domain only.

Thanks.

Hi there,

Please advise on the code modifications to allowing whitelisting 2 domains instead of the above cod which is one domain only.

Thanks.

The code snippet is changed. You can set several email domains in an array.

Thanks a lot, Denis

Hi Denis!!

I'm getting this message after tried to register using your code on my page:
"Notice: Only variables should be passed by reference"

It apparently works but shows that message and break a little the page layout.

My site is running PHP 7.3.25
Could it be the problem?

Thanks in advance!

Is there a way to restrict this not to domains, but to specific TLD's? .gov and .org are needed on a project I am working on.

Tried wildcard in the array, no luck.

function my_submit_form_errors_registration( $args ) {

	// Change error message here
	$message = __( 'You can not use this email domain for registration. Please ensure your department has been whitelisted by the staff.', 'ultimate-member' );

	if ( isset( $args['user_email'] ) && is_email( $args['user_email'] ) ) {
		$email_domain = strtolower( array_pop( explode( '@', trim( $args['user_email'] ) ) ) );
		$pattern = '/^[a-zA-Z0-9\-\.]+\.(gov|org)$/i';
		if ( !preg_match( $pattern, $email_domain ) ) {
			UM()->form()->add_error( 'user_email', $message );
		}
	}
}
add_action( 'um_submit_form_errors_hook__registration', 'my_submit_form_errors_registration', 10, 1 );