What to consider when sending bulk emails is whether or not your email hosting provider has a limit of how many you can send at one time and if whom you are sending has a limit on how many can be received at once form you.

Reason to check is you do not want to be flaged as a sender producing spam. You can then get your domain blacklisted and worse yet your email provider.

I have hosted echange email, the company has a limit of 200 message at one time, If you exceed that they will flag you and ban you from their system.