Limit on size of BCC for mail()?

I'm tinkering with a few options for sending large amounts of customized email to registered users based on their preferences and the activities of other users on the site. Is there anything I should be aware of if I try sending a single email to a large number of users (hundreds or thousands) at once using BCC and mail()? Essentially, I'd use a loop to walk through a MySQL query result to build up a $BCC header to reflect the addresses to which the mail will be sent. Specifically - is there a limit on the number of addresses that I should follow? (i.e. will the server choke - it's a standard Apache/PHP/MySQL setup) And - is there any circumstance (certain mail clients?) that will actually display the full list of recipients, even though I am using BCC? I currently have the system setup to send a separate email to each person, but once this applies to more than a few dozen people (soon), this just won't work. I want the list of recipients to remain secret, out of respect for their privacy. Are there other, more robust, solutions out there? Thanks, Andrew Elliston ------------------------------------------------ Drew's Pad <http://www.elliston.net/drew/> ------------------------------------------------