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I've sent an important email that the recipient claims it wasn't received by them.

They say that they asked their IT team to see if the email was received in their server. According to them the email never reached their server. Also they don't accept the chance that the email was received and marked as SPAM.

Shouldn't I receive an error message in the case the email wasn't delivered?

Is their any way for me to check if they are telling the truth (it sounds very fishy to me).

Thank you.

  • 9
    Are you the admin of the mail server sending the mail? If yes, read your log file. If not, this is off-topic. And no, you don't necessarily get an error - it's entirely possible a receiving server silently discards mails it classifies as spam. Lesson for the day: Important things don't get send by e-mail. – Sven Dec 15 '14 at 19:49
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    Check the logs in your mail server. – Michael Hampton Dec 15 '14 at 19:49
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    @Sven Yes I'm admin of the mail server that sent the email. – belyid Dec 15 '14 at 19:56
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    You should be able to see from your SMTP logs whether or not the recipients server accepted the email. Deliverability beyond that (to the users mailbox) is their responsibility. – joeqwerty Dec 16 '14 at 3:08
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You can absolutely see in the postfix logs where an email was sent, and whether it was accepted. Here's an example log entry from my mail server which indicates that the message was successfully sent to the Google SMTP servers.

Dec 15 14:21:43 ebony postfix/smtp[2422]: D05BB1D872: to=, relay=gmail-smtp-in.l.google.com[74.125.201.27]:25, delay=1.4, delays=0.08/0.01/0.59/0.74, dsn=2.0.0, status=sent (250 2.0.0 OK 1418674912 h96si7402391iod.11 - gsmtp)

What this doesn't show is what the server did with the email after it was accepted, but this entry alone is enough for you to tell the remote IT dept that your mail was in fact delivered and you can give them the Message ID and the response from their server (in parentheses at the end) to provide evidence!

Good luck.

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    This also gives an exact date and time of delivery, assuming the clocks are synchronized. (Which they should be, because any sane server setup will have its clocks synchronized to a standard time, often UTC but sometimes -- the herecy! -- local time.) That will dramatically cut down on the effort of the remote server's administrators tracking down the email in their logs. – a CVn Dec 16 '14 at 14:34
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No, you won't be able to check this.

Email is a "best-effort" service. There are no guarantees that any given email will actually be delivered. Usually you will get a notification that delivery has been delayed, but that depends on the email software between you and the recipient.

You can check your mail server's log to verify that it got sent, but that's no guarantee of delivery.

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    Well you might be able to verify that the message was accepted by their public-facing mail server (and that might be enough depending on the OPs needs) but yes, that in itself is no guarantee that it actually ended up in someone's inbox waiting to be read. – Rob Moir Dec 15 '14 at 19:51
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There is "Delivery Status Notification" aka DSN - MTA send a little message to the submitter when LDA occurs. But as far as that functionality has been used by spammers, postmasters turns it off. Some modern MTA like exim doesn't have it at all.

From the logs you can know that message from your MTA has been passed to another MTA, but you can't estimate that message will be delivered or relayed. Yo have successfully relay the message outside your zone of responsibility and that's all.

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If you don't have access to the logs of the server you used, you can't prove it for that particular message. Normally, you do get an error message back in case of failure, unless the server thinks it's spam and just discards it.

If the server is unreachable, the sending server will keep trying for a couple of days. You'll get a deferred notice after a few hours.

When you want to have prove of a message having been accepted by the recipient server, you can enable a delivery confirmation (not to be confused with read receipt). Not all e-mail clients support that, though. Thunderbird does (when composing a message, choose options -> request delivery receipt or something). A lot of e-mail servers respond to the request for a receipt and you'll get a message back that the message was delivered to server xyz.

  • OP is the admin of the sending SMTP server, so presumably has access to the SMTP logs. See the comments on the question. – a CVn Dec 16 '14 at 14:35

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