it really depends on your hosts limits. every host is different.
you should find out from the host what there mailing limits are and adjust the mail timings to accommodate.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.