On 7/25/2017 7:42 PM, /dev/rob0 wrote:
Oh, I disagree. The best thing to do is to reject anything you're unwilling/unable to deliver. You're not causing any bounces; if a connecting client does generate a bounce for your rejection that is THEIR problem; or in the case of a human sender, that is the way to avoid mail loss.
We can debate RFC's all day but the reality is that we are dealing with people not following the RFCs like spambots. They will just retry and if you do any type of queue and check, then you can cause backscatter, etc.
My advice remains the same if you have mail you are giving a 5xx that is retrying. Giving it a 5xx is the correct answer. If that doesn't work, you will find you need to 2xx it and silently discard.
As mentioned, we do this for viruses in particularly to rid the world of them. I'm sure it breaks an RFC in letter but not in spirit as it's my job to avoid viruses getting through and sometimes they are looking for blowback messages to carry the payload.
Regards, KAM
