Shamim's Plugins

Please follow https://www.shamimsplugins.com/docs/front-end-pm-pro/troubleshoot/license-keys-not-activating/

Add following code in your theme’s (child theme’s if you are using) functions.php and keep there.

add_filter( 'cron_schedules', function( $schedules ){
	$schedules['every_minute'] = array(
		'interval' => MINUTE_IN_SECONDS,
		'display'  => __('Every Minute', 'front-end-pm'),
	);
	return $schedules;
});

Then add following code in your theme’s (child theme’s if you are using) functions.php. Then refresh your website couple of times then remove following code.

add_action( 'init', function(){
	if ( wp_next_scheduled( 'fep_pop3_event' ) ) {
		wp_clear_scheduled_hook( 'fep_pop3_event' );
	}
	wp_schedule_event( time(), 'every_minute', 'fep_pop3_event' );
});

I have temporarily fixed it.
It needs more testing. After testing i will include this fix in next version of the plugin.

Please send using https://www.shamimsplugins.com/sensitive-information/
(admin, normal user and FTP credentials)
Use any email address to create account as that is not important here to receive email.

You can use shortcode https://www.shamimsplugins.com/docs/front-end-pm/shortcode/fep_shortcode_new_message_form/ which support ajax message submit.

Main new message send page does not support ajax yet.

No attachments received. Please send to my email (if you know) or contact through https://www.shamimsplugins.com/contact-us/

Does that error shows initially when page load or it shows when send message?
Can you give me of your message page url? (also a test account credentials to try send test message). If yes please send using https://www.shamimsplugins.com/sensitive-information/