[Top] [All Lists]

Re: [ietf-smtp] SMTP Greylisting Retry Hints + PRDR

2019-02-08 03:43:54
On 07/02/2019 22:20, Dilyan Palauzov wrote:
Strictly speaking the delivery for all recipients does not have to be delayed.  
The server can deliver promptly the messages to all deserving recipients, 
memorize the Message-Id and the per recipient response, and in subsequent 
transactions communicate the status per recipient.

So, you're suggesting delivering the message to the recipient, even though you've said it's been rejected?

That's not standards compliant... You don't KNOW that the sender is going to retry it, and if it does, you don't know if it'll use the same Message-Id, so the recipient may receive a message that the sender thinks they didn't, or they may receive multiple duplicates, or something else. You can't deliver it until/unless you say you'll deliver it.

The problems with the idea of 4xx rejecting recipients with different rules are that you really don't know what the sender is going to do, you are essentially removing the ability to send mail to multiple recipients at once, and you are adding load everywhere - a message sent to 100 people at the same domain potentially has to be sent 100 times rather than just once (even if all recipients will accept it), and there have to be 5050 recipient checks rather than just 100, etc.

Is it that big a deal? If the recipient doesn't want the message, just accept it and quarantine it... That'll may even cut down on support calls - when a message is sent 'To: bob(_at_)example(_dot_)com, kate(_at_)example(_dot_)com', and Kate receives the message, but Bob, who is sitting next to her, doesn't and has no idea why because you PRDR rejected it because of a rule that Bob turned on and didn't understand. (Or doesn't receive it until a few hours later (if at all, if the sender times-out), because he HASN'T got a *relevant* rule enabled, but does have some irrelevant slightly different setting from Kate).


Paul Smith Computer Services
Tel: 01484 855800
Vat No: GB 685 6987 53

Sign up for news & updates at

ietf-smtp mailing list

<Prev in Thread] Current Thread [Next in Thread>