Limit in mySQL DB or PHPmail() function?

Okay, so i setup a form to send out emails. I don’t have to worry about the spam problem, this isn’t a public form for anyone to fill out, instead you have to be logged into a site to use it, only two of us have the login info, and we use the form to send out emails to a list of customers. These customers’ names and email addresssed are in a DB table (named “customers”). The mail form pulls the list of customers and concats them into the $to line. I wrote this code about 2 years ago and it worked fine until about a month ago. Now, nothing happens when you submit the form.

I’ve recently removed all of the subscribers from the mySQL db table and inserted only my email. Now the form works again. So is there a limit to the number of subscribers the $to line can pull? A limit on the $to variable?

I checked to make sure that none of the subscribers had any “odd” characters in their name or email address that could throw an exception in the code. so…

oh, and in the mysql table “Customers”, both the ‘name’ and ‘email’ columns are listed as VARCHAR.

Sorry if this is a lot of info, just wanted to give the experts here plenty to work with…