On 01/06/2023 21:37, Julian Bradfield via Exim-users wrote:
> In response to the recent RCPT-flooding attacks, I changed my
> acl_check_rcpt verification check to say:
> deny
> domains = +local_domains
> !local_parts = postmaster
> !verify = recipient
> message = Unknown user
> delay = 5s
>
> When I test non-existent addresses with a dummy smtp session using
> exim -bh
> then I see the delay being applied:
>>>> check delay = 5s
>>>> delay modifier requests 5-second delay
>>>> delay skipped in -bh checking mode
>
> However, in the exim log file I'm still seeing 99 denied RCPT commands
> all with the same timestamp.
>
> How can this be?
acl_check_rcpt's deny applies to the RCPT not the connection. This is
like if there is one non-existent recipient in a batch then only that is
denied and the rest are delivered. In your case it tests 99 and denies 99.
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