sending mail after 200 mail was stopped

hi all
when i was send a newsletter by simplenews (using smtp module for send) after sending 200 mail was stopped and drupal records these errors for each failed sent:
newsletter 2008-11-19 00:27 Newsletter شماره 52 could not be sent to ... Anonymous

smtp 2008-11-19 00:27 Error sending e-mail from info@itpoultry.com to ... Anonymous

php 2008-11-19 00:27 fputs(): supplied argument is not a valid stream ...
(full error is: fputs(): supplied argument is not a valid stream resource in /var/www/html/modules/smtp/smtp.module line 2110.)

please help