[CentOS] postfix pb with mass emails

> I tried smtp-sink on another port and found that phpbb was the cause of
> the problem.
> phpbb did several connections to the smtp-sink and sent multiple emails
> with more than 50000 recipients instead of 3500.
> When I sorted the smtp-sink output, I could see recipients duplicated
> multiple times.
> 
> Conclusion postfix works great! phpbb sucks!

Now I wonder what is wrong with phpbb...is yours modified at all?