wordpress sending Multiple mails on post publish - wordpress

Question

What I am trying
I need to send a mail to a user when a file has been uploaded to that user. I'm using a custom developed plugin to achieve this. I'm using postman SMTP for sending mails.
The file is added as a post here. The problem is when I publish it sends around 80+ mails to the assigned user in which only 1 mail contains the correct information. Other mails are all blank with just static predefined mail content.
How to fix this?
Code
add_action('save_post', 'upf_save_post');
function upf_save_post($post_id, $post = null) {
global $post;
/* --- security verification --- */
if(!wp_verify_nonce($_POST['wp_upf_nonce'], plugin_basename(__FILE__)))
return $post_id;
if(defined('DOING_AUTOSAVE') && DOING_AUTOSAVE)
return $post_id;
// if invalid $post object or post type is not 'userfile', return
if(!$post || get_post_type($post->ID) != 'userfile') return;
$user_info = get_userdata($_POST['upf_user']);
add_post_meta($post_id, 'upf_user', $user_info->user_login);
update_post_meta($post_id, 'upf_user', $user_info->user_login);
// Make sure the file array isn't empty
if(!empty($_FILES['upf_file']['name'])) {
// Setup the array of supported file types. In this case, it's just PDF.
$supported_types = array('application/pdf','image/png','image/jpg','image/jpeg','text/plain','text/html','application/msword','application/vnd.openxmlformats-officedocument.wordprocessingml.document','application/vnd.ms-excel','application/vnd.openxmlformats-officedocument.spreadsheetml.sheet','application/vnd.ms-powerpoint','application/vnd.openxmlformats-officedocument.presentationml.presentation',);
// Get the file type of the upload
$arr_file_type = wp_check_filetype(basename($_FILES['upf_file']['name']));
$uploaded_type = $arr_file_type['type'];
// Check if the type is supported. If not, throw an error.
if(in_array($uploaded_type, $supported_types)) {
$upf_file = get_post_meta($post_id, 'upf_file', true);
if ($upf_file) {
$upf_file_path = WP_CONTENT_DIR.'/userfiles/'.$upf_file['file'];
if (file_exists($upf_file_path)) unlink($upf_file_path);
}
// Use the WordPress API to upload the file
$upload = wp_handle_upload( $_FILES['upf_file'], array( 'test_form' => false ) );
if(isset($upload['error']) && $upload['error'] != 0) {
wp_die(__('There was an error uploading your file. The error is: ' . $upload['error'], 'user-private-files'));
} else {
// Update custom field
$upload['file'] = substr($upload['file'],stripos($upload['file'],'wp-content/userfiles/')+21);
add_post_meta($post_id, 'upf_file', $upload);
update_post_meta($post_id, 'upf_file', $upload);
} // end if/else
} else {
wp_die(__("The file type that you've uploaded is not supported.", 'user-private-files'));
} // end if/else
} // end if
if ($_POST['upf_notify'] == '1') {
if( get_post_meta($post_id, 'email_sent', 'true') != 'yes' ) {
$upf_file = get_post_meta($post_id, 'upf_file', true);
$email_subject = get_option('upf_email_subject');
$email_msg = get_option('upf_email_message');
$email_msg = str_replace('%blogname%', get_bloginfo('name'), $email_msg);
$email_msg = str_replace('%siteurl%', get_bloginfo('url'), $email_msg);
$email_msg = str_replace('%user_login%', $user_info->user_login, $email_msg);
$email_msg = str_replace('%filename%', basename($upf_file['file']), $email_msg);
$email_msg = str_replace('%download_url%', get_bloginfo('url').'/?upf=dl&id='.$post_id, $email_msg);
$cats = wp_get_post_terms($post_id, 'file_categories', array("fields" => "names"));
$email_msg = str_replace('%category%', implode(", ", $cats), $email_msg);
$headers[] ='From: "'.htmlspecialchars_decode(get_bloginfo('name'), ENT_QUOTES).'" <'.get_option('admin_email').'>';
wp_mail($user_info->user_email, $email_subject, $email_msg, $headers);
add_post_meta($post_id, 'email_sent', 'yes', true);
}
}
}

Answer 1

This may occur because before actually save post, WordPress itself fire save_post action to save post revision.
// If this is just a revision, don't send the email.
if ( wp_is_post_revision( $post_id ) )
return;
Wordpress fire this save_post action on every page status
like on revision, draft, publish, pending
you should check these condition inside your save_post action as per your working.
check the code here
https://codex.wordpress.org/Plugin_API/Action_Reference/save_post
so you should check