Free email providers, such as Gmail, Hotmail, Yahoo! Mail and AOL Mail, usually offer free SMTP email delivery feature and they are the most commonly used channel to send mass emails.
When using the free service, you should be aware of the send limits and rate limits imposed by these free email providers. Through using well-recognized mass mailing software and configuring it properly, you can easily go over the limits and save significant cost.
The following data is mostly collected from the official sources (namely, the official websites of Gmail, Hotmail, Yahoo! Mail and AOL Mail). But your email service provider may change its mailing policy without any prior notification. It is suggested you always contact your email service provider and ask about the most updated SMTP email send limits and send rate before proceeding with your email marketing campaigns.