Author: Simon Arlott Date: To: exim-dev Subject: Re: [exim-dev] [Bug 2341] delay_warning failing to send messages
On 06/12/2018 00:02, Jasen Betts via Exim-dev wrote: > NDRs go to the envelope sender, so they will bounce back to a single
> address (per message), but there can be several "delayed" messages and
> a single bounce (retry timeout exceeded) for each input, so that
> provides small-scale amplification, until the timeout is reached,
> after that no amplification.
>
> where available SPF is one mitigation for this. It prevents the attacker
> from forging the sender address.
Alternatively, set delay_warning_condition to only send warnings if the
email was sent by one of your own users.
