On 14 Jun 2011, at 05:24, Phil Pennock wrote:
> On 2011-06-13 at 00:32 +0000, Michael Jimenez wrote:
>> So I've been looking at my mail server mainlog for the past couple of days watching mail come in and out, I've noticed that this Microsoft address keeps failing to verify:
>
> You're using sender *callout* verification to systems not under your
> administrative control. This is regarded by many as abusive, and will
> get you placed on various blacklists.
Is that true? I've not experienced it, in several years.
> The larger providers have rate-limits and other DoS filters; so when an
> MSN address is spoofed and you keep hitting their mail-servers with
> checks on mails they didn't send, you'll exceed ratelimits and get
> fast-failed: they're rejecting you attempting to deliver to them, which
> you're interpreting to mean that the address is invalid.
That's not likely to happen. Exim's result caching means you're not going to be making frequent callouts regarding a single address. In theory, it could happen if spammers were attempting to deliver to you from many different addresses in the same domain, in rapid succession. However, you could -and should- mitigate against that by doing callouts late.
> Sender callouts are best suited for use to systems under your own
> control.
--
Ian Eiloart
Postmaster, University of Sussex
+44 (0) 1273 87-3148
