Email Sending Limits
What Email Sending Limits Are and Why Hosts Set Them
Email sending limits are caps on how many messages an account or server can send within a set period, such as an hour or a day. On shared hosting they are a common way to control abuse and protect the reputation of the server's shared IP address.
On shared hosting, many websites send from the same outgoing mail server and the same IP addresses. If one account starts sending spam or a large unsolicited campaign, mailbox providers may filter or block mail from the whole address range. A cap on each account limits the damage any single site can do to the others. Repeated abuse can also lead to listings on a email blacklist.
Limits are usually applied per account over an hour or a day. The exact figures vary by provider and are normally stated in the hosting documentation, so they should be checked rather than assumed. The difference between shared and separate mail services is covered in email hosting vs web hosting.
What Happens When a Sending Limit Is Exceeded
When an account goes over its limit, the server typically refuses further messages with a temporary or permanent error. Some messages are queued and delivered in a later period, while others fail immediately. A website may show no error at all, which makes the problem hard to notice, because many contact forms and notification systems simply log the failure.
Repeated overruns can lead to a temporary suspension of outgoing mail. A site that sends a large volume of messages should therefore consider a dedicated sending service instead of relying on shared hosting. One common approach is described in what an SMTP relay is and when you need one.
A Newsletter That Reached the Hourly Cap
A club sends a newsletter to 3,000 members through an email account on its shared hosting. The hourly limit is reached after the first part of the list. The remaining messages are either deferred to later hours or rejected, so some members receive the newsletter much later than others. The club then moves the newsletter to a bulk sending service, which handles the volume, and keeps the website's account for ordinary mail.
Frequently asked questions
Why do shared hosts limit outgoing email?
Shared hosts limit outgoing email to protect the reputation of shared IP addresses. Many customers use the same servers, so one account sending spam or large bulk mail can get the whole address range listed, which affects every site on it.
Do sending limits apply to incoming mail?
No. Sending limits control outgoing messages only. Incoming mail is not usually capped in the same way, although a full mailbox can cause incoming messages to bounce. Mailbox size is a separate matter from how many messages an account may send.