When we talk about a private SMTP, we are referring to the email server provided by your hosting provider or contracted by you yourself. This server allows sending messages in an authenticated manner, but always within the rules imposed by the provider.
Why are sending limits in place?
Providers set limits to:
Prevent abusive use (sending spam).
Protect the IP/domain reputation.
Maintain server stability.
In practice, if a provider limits to 100 sends per hour/day, any attempt to exceed that will result in blocking, failure, or delay in sending.
Bulk sending
Bulk sends (like newsletters to thousands of contacts) are generally not allowed on common SMTP servers. This is because identical emails sent to many recipients raise suspicion of spam and can harm all the provider's customers.
How to send in bulk correctly
If you need to send campaigns to thousands of contacts, the ideal is to use a provider specialized in blasts such as:
Amazon SES
This service was made to handle high volume, deliverability, and sending reputation.
