Plugin is defining pluggable
wp_mail() function. My idea was to check if function is defined already and throw warning if other plugin beat me to it.
However this warning causes issues on activation. As far as I understand during normal operation plugin is loaded before
pluggable.php but for the purpose of activation check it is loaded after pluggables.
What would be the robust/proper/suggested way to implement such check for pluggable function? There is no obvious (for me) way to distinguish activation and handle it separately.