ISP port blocking practice

Fri Oct 23 01:46:52 UTC 2009

On Thu, Oct 22, 2009 at 6:29 PM, Justin Shore <justin at justinshore.com>wrote:

> I can also speak from experience from the enterprise customers of the
> consulting side of my SP that I worked with before returning to the SP.  Not
> a one of them made use of the MSP port.  The vast majority, I'm sorry to
> say, used Microsoft Exchange which to the best of my knowledge doesn't
> support RFC2476.  I did a little Googling just now and couldn't find any
> hits to say they did either.  Some utilized RPC-over-HTTP. Most at the time
> didn't, requiring direct SMTP access or VPN.
>

Depends what you mean by "support RFC2476".

Exchange most definitely supports message submission on port 587.  Whether
it supports RFC2476 to the letter in terms of other requirements I don't
know, but submission as a "client access" mechanism is fully supported, with
all the usual defaults you'd expect (eg, auth required)

Of course, that doesn't mean that it'll be enabled in a specific
environment, or even if it is enabled, that it will be exposed from the
firewall.  Most larger corporates will be using Outlook with Exchange, and
thus may only support RPC-over-HTTP as you've stated.

  Scott