Unable to email more than 5 recipients

I have a set of global filters setup to give me some wildcard filtering which is not quite working but before I ask for an additional feature I am trying to eliminate user ignorance and perhaps failing. My aim is to enable an email to user1-anything@mydomain.dom to get sent to user1's mailbox. I have managed to avoid recursive email delivery issues by delivering to a folder so my filters now are: Rules: \b(?i)user1[A-Za-z0-9._%+-]+@mydomain.*\b> Actions: [As an aside my ISP had raised the filter issue with cpanel when I was simply forwarding the email and the answer came back from my ISP support: "According to CPanel the only reason why its displaying the error message its because the email you want to send the emails to are included in the regex which would cause a loop, adjusting the regex to match everything but the mailbox or adding another comparison such as if $h_to: does not contain "fred@domain.co.uk" should allow you to make the necessary changes and continue to use the rules you have setup." That did not work as it still thought it was a recursive issue but delivering to a folder does work, well almost] That works really well with two exceptions: 1. If I email more than 5 recipients@mydomain.dom then email vanishes somewhere in a loop, don't know where. Up to 5 works fine and it is any 5, checked that. 2. I have an issue with bcc not working when there are other recipients@mydomain.dom but I will pose that query in a separate thread Any idea why I can only email 5 recipients and everything falls over after that?