[imp] error message on client side

[hwetzler at comcast.net]

I am not the administrator nor did I install any of the software for a friend of mine. However, he is asking why he is getting thousands of error messages stating something to the effect that he has exceeded his concurrent email attempts. His web site is http://liglazing.com/index.php and his email is dana at liglazing.com. There are two emails associated with this site and they both get the same errors. It is preventing him from being able to email anyone. Any thoughts on which end this is happening (client or server) or why? 

tks