the status report of the newsletter plugin seems to be buggy when it comes to PHP memory limit. We set ours to 256 MB (.htaccess). We can confirm that by phpinfo(). However, the newsletter status report shows a warning, since we don’t have the correlating rule in the wp-config.php (which we don’t need). Could you fix that?
In wp-config.php limit is set to 128 MB, in php.ini also set to 128 MB and other memory usage plugins correctly show the limit of 128 MB while the check in the newsletter plugin persists that the limit is set to 40 MB.