"Will I get blocked by my ISP/ESP if I send 1,000 emails per day?""How many emails can I send out per day?"… These are the frequently questions that 1and1Soft receives almost every day. Most of these customers are seeking the cheapest way to send out mass emails, and using free email services from Gmail, Hotmail or Yahoo! Mail.
The answer is: it depends.
Even though, officially, most email service providers have announced the daily quota, or sending limit of their SMTP server, the actual number may still vary by each email account's reputation score.
The sender score / reputation score is usually calculated by the bounce-back rate, spam rate imposed by the recipients and keywords filtering. If you send out too many emails within a short period of time that contains a lot of spam sensitive keywords, your reputation score is at risk. Next time, your ESP will limit your sending quota and lower your email deliverability.
In 1and1Mail, you can easily control how many emails you can send out per day. When you reach the limit, 1and1Mail will automatically stop sending, and resume after 24 hours. Try to send fewer emails per day at the beginning. When you gradually build up your reputation with your ESP, you can increase the number later.