Shamim's Plugins

Sorry for delayed responses.
This plugin is not abandoned.
Hope i will be able to provide support regularly as before from now on.

Can you provide me your website url where you are trying to add the license?

This plugin do not use email address but username. So may be your other plugin use email address to generate username. They remove @ symbol when they create username.

Can you give me a screenshot where you are checking and what error you are getting?

By default only admin can send announcements. If you want any other role to allow please follow https://www.shamimsplugins.com/support/topic/create-announcements/#post-26559

You can use fep_action_message_after_send hook to save message id in database.
You can find some examples in https://www.shamimsplugins.com/support/search/fep_action_message_after_send/

I am trying to fix it. It may take some time.
In the meantime you can use different display name for the user. Use following code to show full name instead of just first name

add_filter( 'fep_filter_show_which_name', function( $which ){
	return 'first_last_name';
});

This plugin provided “Every 15 minutes” (fep_15_min) interval. Others are added by your other plugins/themes. So you can switch back to this.
event name is fep_email_interval_event.
Also please take note message get priority over announcement when sending queue emails. If you send message for more than 5 users (default set) it usages queue to send emails.

You can see class-fep-email-beautify.php file (email_interval_event_callback method) for code.

Please use like following

function mail_icon( $user ) {
    ?><a href="<?php echo fep_query_url( 'newmessage', array( 'fep_to' => $user->user_nicename ) ); ?>"><img src="[URL]" /></a><?php
}