This error occurs when you try to send more than 180 emails in one hour. This limit must necessarily be set in a shared environment in order to prevent a single account from compromising the reputation of the server's IP address, making it included in any blacklist.
A blacklist is a public database of IP addresses that are considered dangerous as a source of spam. Once an IP is entered into these databases it will have difficulty delivering its emails to legitimate recipients correctly.
Keliweb shared hosting solutions such as KeliUser, KeliPro and KeliCMS have this limitation in e-mail dispatch. The block, if you exceed the limit, is temporary and your hosting will be enabled automatically to send e-mails again in an hour. In the Cloud Hosting solutions the limit is, instead, 300 e-mails per hour.
To send newsletters and avoid the previous limitation, visit our E-mail Server page to choose the perfect dedicated solution for your needs.