Hi @viorelepuran
The scheduling of a post works the same as any wp cron so it would not make any difference if no one visits your site. I think the right way to go is to create your own cron job as you initially thought.
To make wp cron more reliable is actually pretty simple if you have access to cron on your server/hosting.
https://tommcfarlin.com/wordpress-cron-jobs/
I don’t know what “Advanced Custom Fields Contact Forms” is but I assume it’s a third party plugin. I will assume it creates a CPT which all the submissions are saved to as posts.
I would create a cron job that triggers a function. In the function you query the submissions for date values where the date is in two days from today. Then in the loop you find the users email and send out an email using wp_mail. It’s all fairly simple if you’re familiar with PHP 🙂
Here’s how to get a date two days from now:
$date = date('Ymd', strtotime('+2 days'));
and a query
$upcoming_query = new WP_Query(array(
'post_type' => 'submissions' //whatever it is
'meta_query' => array(
'key' => 'acffield',
'value' => $date,
'compare' => '='
),
'posts_per_page' => 100,
'no_found_rows' => true,
'update_post_term_cache' => false
));
