Problem with timing to send mails, sleep of 15 minutes

[eluser]Rubiz'[/eluser]
Hello!!

Well, I'm with a problem, more logical than freak...

I built a logic script for sending mail marketings, but my host cant send more than 50 once, it must be:

- send 50...
- wait 15 minutes
- send more 50...
- wait more 15 minutes..

This is relatively ease to do, I made it with the sleep() PHP function, to make the waiting 15 min. but I'm getting this error: MySQL server has gone away.

I would like to know what s#$%t is that, and how I could solv this problem... anyone has any idea?

Thanx...