Daily Email Sending Rate of a New Domain - AotSend

AotSend's Unlimited API Rate Strategy

AotSend adheres to an unlimited rate policy for sending emails. However, it is important to note that while sending is not rate-limited, the receiving mail servers may impose their own limits. For example, each mail server may have restrictions such as the number of emails it can receive per minute from a specific domain or IP address.

Why Do Mail Servers Impose Rate Limits?

Mail servers generally apply rate limits to domains to prevent spam and protect their users. For instance, Gmail may impose a limit of sending one email every 20 to 60 seconds for new domains. If this limit is exceeded, you may receive numerous bounce-back emails, indicating delivery failures. Gmail does this to avoid large volumes of emails from domains with low reputations, which could be associated with spam. Gmail prioritizes user experience and prefers to err on the side of caution with new domains, which could result in rate limits and delivery failures. Other mail servers, such as QQ Mail, 163 Mail, and Outlook, also have their own receiving frequency limits.

Typically, rate limits for new domains are not higher than 10,000 emails per day. Specific limits can vary by domain, IP address, and mail server, and some restrictions may be dynamically calculated, making exact numbers difficult to determine.

When sending to a mixed list of email addresses, such as those from QQ Mail, Gmail, and Outlook, it's essential to monitor whether any individual mail server's rate limits are exceeded.

How to Improve Email Sending Rates

If emails are bounced back due to abnormal sending rates, monitor the complaint rate or spam report rate. As long as the complaint rate stays within the acceptable limits of the mail server (some sources suggest 0.2%, though this is not publicly confirmed), the bounce-back issue should be manageable. With stable email sending practices, domain reputation will gradually increase, allowing for higher email volumes to be successfully delivered over time, creating a positive feedback loop. After an initial warm-up period, daily sending limits for a single domain can increase progressively.

Cold Start Daily Sending Strategy

A cold start refers to sending emails from a new domain without prior reputation or warm-up. When a new domain cannot meet the daily sending requirements, using multiple domains in rotation can be an effective strategy. For example, if one domain can send 5,000 emails per day and the goal is to send 50,000 emails daily, configure 10 domains to rotate sending.