You should never be sending bulk email through your email client or general hosting provider unless you are well versed in the email business. General hosting are not optimized for sending large quantities of email and you'll find yourself blacklisted with major isps and corporate networks in no time at all (yes this can even happen with a few hundred emails). Sending one email at the expense of delivering anything in the future is a loss.
Thus you need an email provider. They are not free but they are also very cheap. This is the cost of the marketing benefit that is your email list.