Since there's been a lot of drift on this topic and I'm not talking about IPv6, DNSSEC, or delivery to Gmail....
For NDRs and DSNs to be truly useful to an ESP, we tend to break them down into more buckets than two. Hard bounce/invalid (do not retry, generally a 5xx) Soft bounce (temporary and related to a specific email address, generally a 4xx, try again later during the current send, Yahoo uses 4xx where we would expect a 5xx such as with some of the traffic shaping deferrals) Technical (DNS failures and the like, try again later, generally 5xx but depends on the reason) Spam or block (stop for this send, try this recipient on future sends, mix of 5xx and 4xx) Unknown (parser doesn't have an appropriate string, manual review and update of systems required) The primary challenge from a technical perspective is making sure that any changes in friendly language in an NDR or DSN is updated on the bounce parser. We do tend to MOSTLY ignore 5xx and 4xx, but that is more a function of how those are used by mailbox providers. The desired end result is that we send all email in a manner that is acceptable to each mailbox provider based on their (technical and personal) feedback and desired rate limits. Extended codes are useful, when you know how a provider applies them, but again, there is such variation in the how codes are applied and when that it's all but impossible for someone not steeped in the intricacies of RFCs to interpret them properly. Not all customers have access to people who spend a lot of time going over bounces and making them actionable. A lot of our job as an ESP is taking the technical and making it understandable to someone who doesn't have the training and background on RFCs and "proper" technical jargon. I've spent the last 18 years or so going over NDRs and DSNs and some still throw me. Filters are also increasingly more complex and we see the same bounce used for multiple purposes, so cross-referencing which bounces happen where is becoming more important to understanding the root issue for a customer. Cheers, Karen On Fri, Dec 11, 2015 at 9:06 AM, Ian Eiloart <i...@sussex.ac.uk> wrote: > I wonder why they don’t use the terminology from the RFCs: "reject", > "defer", "non-delivery notification", "delay notification"? > > As it is, when you say "Hardbounce", I don’t know whether you’re referring > to an SMTP 5yz reply (a rejection) by the receiving MTA or an rfc 3461 > "failed" DSN sent to the sender to alert them to the problem. > > Similarly, I don’t know whether "softbounces" means an rfc5321 temporary > failure reply , or an rfc 3461 "delayed" DSN. Neither of which mean quite > what you said, since the intention is that the sending MTA will retry for a > period. The sending MTA can’t use other means. If the original sender tries > again, then the recipient will get duplicate messages when the fault is > resolved. > > If the ESP is good, the the sender will have access to a support team, so > all faults should be actionable. > > > > On 11 Dec 2015, at 11:59, David Hofstee <da...@mailplus.nl> wrote: > > > > That’s why, in ESP parlance, there are two sorts of bounces, to keep it > simple: > > - Hardbounces: The recipient address does not work. Contact > through other means. > > - Softbounces: This email did not arrive. Try again later or > contact through other means. If this keeps happening the address > effectively does not work. > > > > What else is there to do? The sender might be curious to what the reason > is (if the bounce is even telling you that) but it does not change the > outcome or the call to action. The only things that are actionable for a > sender, in a message, is when the content gets unacceptable (spam, too big). > > > > We have about 30 categories to explain what type of error occurred > (available on request). > > > > Met vriendelijke groet, > > > > > > David Hofstee > > Deliverability Management > > MailPlus B.V. Netherlands (ESP) > > > > Van: mailop [mailto:mailop-boun...@mailop.org] Namens Brandon Long > > Verzonden: donderdag 10 december 2015 22:23 > > Aan: Dave Warren > > CC: mailop > > Onderwerp: Re: [mailop] Delivery to gmail via IPv6 > > > > I was just discussing this issue with our support folks, and we're > looking at improving ours for this reason. We also see a remarkable number > of our NDRs marked as spam, especially by those whose primary language > isn't English. > > > > We'll definitely still include the technical information, but it'll be > further down. > > > > And we'll do our best with handling the remote server's error messages, > but ugh. It's too bad that the extended status codes are still so > generic... though, as our tech writer and ux folks pointed out, really, all > the user cares about is "did I do something wrong? Is there something else > I can do?" > > > > Brandon > > > > On Thu, Dec 10, 2015 at 12:18 PM, Dave Warren <da...@hireahit.com> > wrote: > > And unfortunately the friendlier they are, the less useful they usually > are. > > > > The ugly ones are the only ones that are useful, but for whatever > reason, it's beyond MTA developers to start with friendly messages with a > "Troubleshooting information below" that contains a useful transcript. > > > > As a techie, I appreciate the info, but the reality is that unless you > expect the sender to take some action, transient error messages aren't > usually useful. We've scaled back the transient failures that we send, at > most you get a single transient and single permanent error, and even still, > I question the value of the transient error since the user can't actually > do anything (and nor does forwarding it to support@ help). Of course, we > also allow users to view the SMTP queue for all messages involving their > account for those who care, so that might skew my viewpoint. > > > > I'm not a fan of the current trend of using permanent error codes in > SMTP for what might well be transient errors (DNS problems, for example), > but at the same time, as a sender, I don't see any value in retrying more > than 24 hours. > > > > It's tough to balance user expectations though. > > > > -- > > Dave Warren > > http://www.hireahit.com/ > > http://ca.linkedin.com/in/davejwarren > > > > On 2015-12-10 10:43, Franck Martin wrote: > > It also has to do with people not understanding DSN. Seriously they are > ugly and hard to find the relevant information in them... > > > > > > > > > > _______________________________________________ > > mailop mailing list > > mailop@mailop.org > > https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop > > > > _______________________________________________ > > mailop mailing list > > mailop@mailop.org > > https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop > > -- > Ian Eiloart > Postmaster, University of Sussex > +44 (0) 1273 87-3148 > > _______________________________________________ > mailop mailing list > mailop@mailop.org > https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop > -- Love is strong yet delicate. It can be broken. To truly love is to understand this. To be in love is to respect this. ~ Stephen Packer ~
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