How to prove no email was sent to me from a certain email address
 

Paid through paypal for a service where the payee sends an email to me. No email was ever received. When I raised the paypal dispute, the payee claimed they had sent the email to me.

I know who their ISP is from an older email from them. Can the ISP confirm or deny that an email was sent from them to my email in the period given?

Maybe. But you'd need the sender to provie you the Message-ID and date/time headers from the sent mail. Even then, the ISP probably won't keep such records and if they do they might not look up the answer even for a fee. For what it's worth if either end involves M$ Exchange + M$ Outlook then you are probably looking at double-digit mail loss anyway.

Can't the ISP search by my email address?

Only if they save the metadata. There are legal and economic liabilities in doing that. Then even if they have the data another question is if they will search it for you.

However, the onus is on the sender to prove they sent the message. They will provide you with the exact Date header along with the exact Message-ID header as preliminary proof. If they do not, then you can safely conclude that they never sent anything.

I thought the header is trivial to forge out of the older email they sent me.

Can my yahoo email service prove what is wanted if asked?

Yes, the headers are trivially easy to forge. They only are needed to show where the ISP should look in their own logs --> if they have the logs and --> if they are willing to look in those logs on your behalf. And even if the answer is yes to both, the larger the ISP the more they have to sift through.

You probably won't get more information from the forum on this matter. You should turn to the ISP and ask them.

Again the obligation is on the alleged sender to prove to you that they actually sent the message.

Just found that by default in paypal you do not win disputes for services "because they are difficult to prove" so there is no incentive for the payee to contact their ISP for evidence.

However, I can hopefully contact my email provider, yahoo. Can yahoo prove anything if they want to? Ie from a purely technical point of view, is email delivery/notification of failure guaranteed? And therefore the payee cannot claim it went missing because they would get notified of the failure and try again?

There is no real notification of mail delivery or failure thereof. That's why so many managers and C-level execs like M$ Outlook / M$ Exchange, because it gives them plausible deniability regarding the mail they didn't send but claim to.

As far as what Yahoo can or will do for you, see #4 above. The longer you wait though the less likely they are able to help even they a) could and b) are willing to. Again, there's not much help any of us on the forum can provide in this, it's time for you to contact the ISP.

Sorry to hear that this is yet another Paypal dispute. They burn a lot of people, some after just using it once or twice. However, the word does not really get out or else people close their ears to the problems.

Thanks for the input but can you please not talk about the non-technical side.

What does the smtp protocol do if a link fails? Why would failure not be notified sometimes? Never seen a failure that did not get notified.

It depends on the which part of the connection you are talking about. If for some reason the sender cannot get through, there are mandatory retries at increasingly long intervals. If the SMTP server is not available or there is no such account, to name two examples, attempts to resend the mail will occur over two days or so before a bounce message is supposed to occur. Sometimes the failure is silent.

The questions about the Message-ID header and Date header of the allegedly sent message can only be provided by the person who is claiming to have sent the message. You need their cooperation for that. Without that data, it will be very much harder to find the alleged message because then it is no longer a known-item search. It's a larger task than just digging through the logs produced by a SME mail server or server pool.

Again, the questions you have about mail logging by your ISP can only be answered by the ISP itself. Please contact them if you wish to pursue your task further. If you do, it would be interesting to hear the results. Again, the longer you wait the more data they have to wade through, if they even have the data. They are unlikely to keep that data. They are more unlikely to keep it a long time. Only the ISP can say what they keep and how long.

I was hoping for a technical approach in this topic, common sense need not be repeated. Smtp is not just between the sender and their isp.

Does anyone know if email delivery or notification of failure is guaranteed, ie if a failure in one of the several servers an email goes through is guaranteed to generate a failure notification to the sender?

Even if an email was sent, it might not have been received. E-mail is not 100% reliable. (The seller should have sent you a message through eBay or PayPal or what-have-you.)

However, I suggest that the two of you (buyer and seller) simply seek in good faith some kind of compromise settlement between you. "The technology went wrong, somehow, this time." Assume that neither party intended any harm to the other, and "work things out somehow." Then convey to the payors what you did work out, and both of you move on.

What are those notifications I get, rarely these days, that an email of mine has failed to reach its destination?

Do you see that such a notification would make any well-intending sender send again or seek other means of communication? So again, what does the SMTP protocol do about failures along the way?

Not much, even assuming the ISP's implementation is fairly complete, which they usually aren't

https://tools.ietf.org/html/rfc3461

https://tools.ietf.org/html/rfc5321

sundialsvcs has a good point and sometimes it is easy to get distracted by the computers and forget what the goal is.

Are you just telling us you've read those two links? And from them you found that errors do not propagate back to the sender?

Btw there are more details to this paypal dispute, that make it obvious no email was sent deliberately as they expected no further business, these are US based but not normal business people. But details why they are such is outside the range of discussions here Does anyone know whether $300 worth of theft is enough to make an attorney handle it automatically without me meeting the attorney and have the police obtain server logs?