How to check “From Email” via WordPress before an email is sent

In wp_mail() there are filters to adjust from address:

// Plugin authors can override the potentially troublesome default
$phpmailer->From     = apply_filters( 'wp_mail_from'     , $from_email );
$phpmailer->FromName = apply_filters( 'wp_mail_from_name', $from_name  );

However they don’t seem convenient for your needs because they don’t provide access to mailer object at the same time.

You are probably better of using action hook further down

do_action_ref_array( 'phpmailer_init', array( &$phpmailer ) );

to check what $From field in it holds and adjust if necessary.