Hello
If you use authenticate email with php (with PHPMailer for example), yes, you will be able to see it in maillog plugin, if it's an mail without any authentication, we retrieve the data in database but actually plugin not show it (we are develop an new release for this you will get it in next days).
There a filter you can search any showed data, but you will not be able to filter if it's an mail sent by php or an mail sent by mailbox for now as there is really no difference for this in maillog.
About notification, our plug-in review country login of mailbox and can sent notification in case of strange login, but not notification about mail volume sent, for this you have plesk mail settings directly.
We constantly try to improve plugin funcionality
Thank you for your interest