Shamim's Plugins

Please use a higher priority to your filter eg. add_filter( ‘fep_menu_buttons’, ‘your_function’, 50 );

You can pass different class for different button. Next version you will be able to pass id also.
In your code you are overriding full button, it will be better if you override just what you need. eg. use $menu['newmessage']['class'] = 'fep-button your_class';

Style (css) file loaded only in message page. You can use wp_enqueue_style( 'fep-style' ); for other pages to show layout correct. But all links will be pointed to the page what you set in Dashboard > Front End PM PRO > Settings > General > Front End PM Page

You can follow following,
1. use fep_form_field_output_fep_pro_to action hook to create a checkbox in “To” field
2. use fep_form_field_validate_fep_pro_to to check if your checkbox is checked, if checked than you can query your group members on the fly and added in $_POST['message_to_id'] as array.
3. You may need to use fep_errors()->remove('pro_to') in fep_action_validate_form hook

Note: I will try to add Group messaging feature in next major version.

Thank you for your nice suggestion. It is already implemented. Next version you will see this feature.
You can try https://github.com/shamim2883/front-end-pm for development version and let me know if you like this.

New filter fep_pro_filter_pre_populate is added here to change the value for next version. Next version will be released next week.

There is no way to delay in email piping. If your server does not delay to send email then this should work immediately.

Do you have cpanel? If yes, then give me access to your webisite(cPanel, website admin & ftp) so that i can try to setup for you.
Please use “contact-form[a t]shamimsplugins.com” email address as admin user so that i can receive email for testing.
Full backup your website before giving me access.