Shamim's Plugins

when message is sent fep_action_message_after_send is fired. first argument is message id of newly created message.

If you want to show only one message then you have to custom code for that. You can use fep_get_message_with_replies() function to retrieve any message and show them anywhere.

You can add remove_action( 'fep_action_message_after_send', array( Fep_Emails::init(), 'save_send_email'), 20, 2 ); just before using fep_send_message()

Your attachment will not be sent with email in your approach.
From my code add_action ('fep_action_message_after_send', 'fep_open_emr_upload_attachments', 10, 3 ); and bellow everything move to above function action_putmessage( $args ) {. That means attachment hook have to be added first.

Let me know.

Please use following (Untested).
let me know

function action_putmessage( $args ) {
	global $out, $admin_user_login;
	
	if( ! function_exists( 'fep_send_message' ) )
	return false;
	
	$sender = fep_get_userdata( $admin_user_login, 'ID', 'login' );
	
	if (!$sender) {
		$out['errmsg'] = "No such sender '$admin_user_login'";
		return false;
	}
	$recipient = fep_get_userdata( $args['user'], 'ID', 'login' );
	if (!$recipient) {
		$out['errmsg'] = "No such recipient '{$args['user']}'";
		return false;
	}
	$message = array(
		'message_title' => $args['title'],
		'message_content' => $args['message'],
		'message_to_id' => $recipient,
		'open_emr_args' => $args, //pass to get in attachment function
	);
	$override = array(
		'post_author' => $sender,
	);
	$message_id = fep_send_message( $message, $override );
}

add_action ('fep_action_message_after_send', 'fep_open_emr_upload_attachments', 10, 3 );

function fep_open_emr_upload_attachments( $message_id, $message, $inserted_message ){
	if ( ! fep_get_option( 'allow_attachment', 1 ) || ! $message_id || empty( $message['open_emr_args']) )
	return false;
	
	$args = $message['open_emr_args'];
	
	$name = isset( $args['filename'] ) ? $args['filename'] : '';
	
	if( ! $name )
	return false;
	
	$size_limit = (int) wp_convert_hr_to_bytes(fep_get_option('attachment_size','4MB'));
	$fields = (int) fep_get_option('attachment_no', 4);
	
	if( class_exists( 'Fep_Attachment' ) ){
		add_filter('upload_dir', array(Fep_Attachment::init(), 'upload_dir'));
	}
	
	$mime = isset( $args['mimetype'] ) ? $args['mimetype'] : '';
	$content = isset( $args['contents'] ) ? base64_decode($args['contents']) : '';
	
	if( !$mime || !in_array( $mime, get_allowed_mime_types() ) )
	return false;
	
	$size = strlen( $content );
	if( $size > $size_limit )
	return false;
	
	$att = wp_upload_bits( $name, null, $content );
	
	if( ! isset( $att['file'] ) || ! isset( $att['url'] ) || ! isset( $att['type'] ) )
	return false;
	
	$attachment = array(
		'guid'           => $att['url'], 
		'post_mime_type' => $att['type'],
		'post_title'     => preg_replace( '/\.[^.]+$/', '', basename( $att['url'] ) ),
		'post_content'   => '',
		'post_author'	=> $inserted_message->post_author,
		'post_status'    => 'inherit'
	);
	
	// Insert the attachment.
	wp_insert_attachment( $attachment, $att['file'], $message_id );
	
	if( class_exists( 'Fep_Attachment' ) ){
		remove_filter('upload_dir', array(Fep_Attachment::init(), 'upload_dir'));
	}
}

You can see Fep_Attachment class. upload attachment is hooked to fep_action_message_after_send action. But if $_FILES[‘fep_upload’] not exists then no attachment will be uploaded. In that case you can see FEP_Email_Pipe class and see how it is done there.

This feature was there in initial versions of this plugin. But for user feedback this feature was removed many days ago. So this feature may not be included.
you can use fep_action_message_after_send action hook to send email to sender if you need that badly.