Re: [exim] greylisting question

On 12/29/2004 20:27, "Andrew" <andrew@???> wrote:

> Hi Everyone,
>
> I have a question about how grey-listing handles multiple rcpt's (to a
> single address) -
>
> eg (SMTP transaction)
> helo me.me
> ...
> mail from: me@???
> ....
> rcpt to: userx@???
> rcpt to: usery@???
> rcpt to: userxy@???
>
> If the MTA (using greylisting) returns a 4xx message to the first user,
> will the sending smtp server stop there (and re-try later) or will it
> also try usery and userxy .... (etc,etc?). If it stops at the first
> 4xxx then with multiple recepients the delay could be days :(

It's impossible to say how every connecting server behaves. There are so
many broken servers, and working servers with broken configurations out
there.

Many do try every recipient. Of those, some give up when every recipient
has been temporarily rejected, others press on with DATA, getting the
RFC-required error code back. Of the latter, some behave sensibly at that
point and others send back a bounce to the sender--these need to be
whitelisted by whatever whitelisting mechanism you use (we use a MySQL
database and Python code that allows very flexible whitelisting).

I haven't seen evidence of a server giving up after the first temporary
rejection, but if there are only 2 or 3 recipients I could easily miss the
footprints.

--John