PHPMailer cannot modify header information

I am continuously receiving a warning when attempting to send multiple emails in a foreach loop with PHPMailer. It sends the first few but dumps the process on the screen along with a warning message:

Warning: Cannot modify header information - headers already sent by
(output started at includes/class.smtp.php:173) in email-test.php on line 70.

Is there a server configuration issue with PHPMailer that I need to adjust? Has anyone else run into this problem?

Assuming you’re not hitting email limits, try slowing the foreach() between sends to slow things down a bit and see how you fair.