wp_mail - send emails after 24 hours from users registration

Question

I have writed a lugin that will send emails after the user completed a custom registration form. I need to send emails after 24 hours from registration, is this possible by using the wp mail function?

UPDATE

Not sure if this can work as expected but I've added as suggested a custom action hooc into the construct of my plugin class in this way

add_action('send_login_credential', array($this, 'send_scheduled_registration_email'));

And into the function that will manage the ause registration approval, I've added the code for the cron in this way

                $user_email = $customer->user_email;
                $num_t = sanitize_text_field( $request->get_param('numTessera') );
                $subject =  'User approved';
                $message = ".... \n";
                $message .= "...: $num_t \n";
                $message .= "...password: \n";
                $message .= "$password \n";              
                //
                wp_schedule_single_event( DAY_IN_SECONDS * 1, 'send_login_credential', array( $user_email, $subject, $message ));

the function that will be called from the custom action hook will only contain the logic to send the email

    public function send_scheduled_registration_email( $user_email, $subject, $message )
    {
        //add_action('send_login_credential', array($this, 'send_scheduled_registration_email'));

        $message_sent = wp_mail( $user_email, $subject, $message );
        if( $message_sent ){
            return [
                'status' => 'ok'
            ];
        }
    }

Is there something I will need to do in the code or it can work?

Answer 1

You can't schedule a future email from wp_mail * but you can use wp_schedule_single_event to run in 24 hours time, and write an action hook handler that calls wp_mail() to send your mail, e.g. something like

wp_schedule_single_event( time() + (60*60*24), 'send_new_user_next_day_email', args( $userId ) );

function send_new_user_next_day_email( $userId ) {
    // look up the user and call wp_mail()
}
add_action( 'send_new_user_next_day_email', 'send_new_user_next_day_email', 10, 1 );

Note that this runs on the WordPress cron system and so will trigger when you next get traffic on the site after the 24 hours are up. You can however set up system scheduler events to trigger cron events even when there's no website traffic - see the wordpress.org cron docs.

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* unless the mail server you're sending through supports it, e.g. Office 365 does, but I'm not sure what mail headers etc. you'd need to set up to do that.

Answer 2

To achieve this, you'd first set up a scheduled task using the wp_schedule_single_event function after the user completes the registration. This will trigger an action 24 hours later, and in that action, you can use wp_mail to send the desired email.

Here's a basic outline to give you an idea:

// Let's say this is your registration function
function your_custom_registration_function($user_email) {
    // ... your registration code ...

    // Schedule the email to be sent in 24 hours
    wp_schedule_single_event(time() + 24*60*60, 'send_followup_email', array($user_email));
}

add_action('send_followup_email', 'send_email_function');

function send_email_function($user_email) {
    $subject = "Hey! It's been a day since you registered!";
    $message = "We're so glad you joined us! Here are some things you might want to check out...";
    wp_mail($user_email, $subject, $message);
}