I have the same question, and that answer is way over my head.
Been using PHp for several months, so havent got that far into it.
I have written a script using mail() to send to a list, and it works with 30 addresses, but I am wondering if it will hold up with 4000+. Will this overwhelm the mail server? Also, if my computer crashes, that stops the process doesn't it. Is that what your answer pertained to? To start it working, then leave.
Thanks
Bob