Re: [ietf-smtp] [Emailcore] Proposed ESMTP keyword RCPTLIMIT

[Ned Freed <[e-mail]>]

> On Mon, 19 Apr 2021, Ned Freed wrote:
> > I'm especially interested in people's thoughts on rate limits. The problem I
> > have with rate limits is, well, how to express them. ...

> A little surveying might be in order.

> I see that Postfix lets you set both the numerator and denominator of the
> rate limit, but the denominator defaults to a minute.  It has separate
> rate limits for connections and messages.

> Exim also lets you set both, the examples use an hour.  The documentation
> says that if you use a large interval that lets people send bursts.

Sounds familiar. Oracle Messaging Server lets you set both; the denominator
default is one hour. 

We store the limits in memcache or Redis so they can apply across mutiple MTAs.
The usual limit is per-IP, but we support per-host and per-domain as well.

The demoninator in PowerMTA is a string rather than a number, possible
values are sec, s, min, m, hr, or h. It supports per-IP and per-host and
probably other stuff; my familiarity here is limited.

I assume the Exim and Postfix limits are per-host, which in most cases
translates to per-IP.

I have to say there's more consistency here than I expected.

				Ned