rate limit number of email messages per connection

This feature request relates to the number of email messages that can be transferred per connection made to the sending server (incl third party smtp auth).

Imagine a fax machine that would call another, and then transmit 10 pages with that 1 call, instead of making 10 separate calls and transmitting each time just 1 message.

As one can see, this is a matter of efficiency (connect, disconnect, checks, etc) and therefore saves both sides resources, while giving the ability to set safety controls.

It could come-in handy not just for third party scripts (or scripts that use such), e.g. phpmailer and swiftmailer, but even for the cpanel built-in one: mailman.

Hope you find merit in this proposal and make it part of the email dashboard of cpanel :)