Debug and Logging won’t turn off

I got a lot of warning errors and I turned off both logging and php debug and I still get the same errors. 1.7.2 version

Warning: substr() expects parameter 1 to be string, array given in /home/samyrugema/public_html/wp-content/plugins/postman-smtp/Postman/PostmanUtils.php on line 68

Warning: substr() expects parameter 1 to be string, array given in /home/samyrugema/public_html/wp-content/plugins/postman-smtp/Postman/PostmanUtils.php on line 68

Warning: session_start(): Cannot send session cache limiter – headers already sent (output started at /home/samyrugema/public_html/wp-content/plugins/postman-smtp/Postman/PostmanUtils.php:68) in /home/samyrugema/public_html/wp-content/themes/lifeline/functions.php on line 18

Warning: substr() expects parameter 1 to be string, array given in /home/samyrugema/public_html/wp-content/plugins/postman-smtp/Postman/PostmanUtils.php on line 68

Warning: substr() expects parameter 1 to be string, array given in /home/samyrugema/public_html/wp-content/plugins/postman-smtp/Postman/PostmanUtils.php on line 68

Warning: Cannot modify header information – headers already sent by (output started at /home/samyrugema/public_html/wp-content/plugins/postman-smtp/Postman/PostmanUtils.php:68) in /home/samyrugema/public_html/wp-admin/post.php on line 197

Warning: Cannot modify header information – headers already sent by (output started at /home/samyrugema/public_html/wp-content/plugins/postman-smtp/Postman/PostmanUtils.php:68) in /home/samyrugema/public_html/wp-includes/pluggable.php on line 1179