sending dual newsletters

[ljaques]

I set up a Zencart for a client and it keeps sending two emails to everyone when he sends the newsletter out. This happens about 95% of the time. It's version 1.3.7 on:
Server OS: Linux 2.6.18-238.9.1.el5PAE Database: MySQL 4.0.30-max-log
PHP Version: 4.4.9 (Zend: 1.3.0)
HTTP Server: Apache
Any clues? I can't find any reference to dupes here on the forums. They both come to the exact same email address within a minute of each other.

[kobra]

Very few are running that old ZenCart code base

Additionally, not many are operating on servers with outdated non-supported php & mysql