If you are using a free email service provider, you may not be allowed to send a large number of emails, for example, if you are trying to send out a monthly newsletter to 1,000 subscribers. With a free service, ensure that you check the service provider's rules and regulations if you are attempting to send out a mass amount of emails.
If you are looking to send out bulk emails, you can switch to a paid email service, such as one that will send from your company domain or business domain. With this type of service, you should not have restrictions on how many people you can send to. Just make sure everyone you are emailing has opted in to receive your messages.