Suggestion for Multisite

Trying to see the logic in the installer where it loops over the entire list of blogs.

Instead of looping over the blog ids just install for the current blog, e.g. (this is the older V1 plugin, but the same logic is in the new one)

$blog_id = get_current_blog_id();
switch_to_blog($blog_id);
if(file_exists(MAIL_BK_PLUGIN_DIR. “/lib/wp-install-script.php”))
{
include MAIL_BK_PLUGIN_DIR. “/lib/wp-install-script.php”;
}

Otherwise if you have thousands of sites in a multisite it times out because you are looping and trying to run the installer on every single site.

If the intention was to make it globally installed on multisite, then you should refactor and consider having the SMTP settings the same for every site in the multisite admin.