postfix error handling to not lose the mail

Question

I have a website with a form. When submit the form php sends a mail to a local gateway.

php code looks like this:

$ok = @mail($emailData['to'], $emailData['subject'], $message, $emailData['headers']); 
    if ($ok) { 
      echo "<p>Message has been sent.</p>"; 
    } else { 
      echo "<p>Message could not be sent!</p>"; 
    } 

So when a mail has been successfully sent, the mail.log looks like:

May 11 06:15:01 webserver postfix/qmgr[2280345]: 7B6B0600EF: from=<www-data@webserver>, size=803, nrcpt=1 (queue active)
May 11 06:15:01 webserver postfix/smtp[2573042]: 7B6B0600EF: to=<[email protected]>, relay=192.168.1.250[192.168.1.250]:26, delay=0.06, delays=0.03/0.01/0.02/0.01, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 8478AE11B4)
May 11 06:15:01 webserver postfix/qmgr[2280345]: 7B6B0600EF: removed

However, due to a technical problem, the gateway wasn't reachable and the mail.log looked like:

May  8 06:40:12 webserver postfix/qmgr[1521]: 33890607E6: from=<www-data@webserver>, size=67769, nrcpt=2 (queue active)
May  8 06:40:42 webserver postfix/smtp[1493379]: connect to 192.168.1.250[192.168.1.250]:26: Connection timed out
May  8 06:41:12 webserver postfix/smtp[1493379]: 33890607E6: to=<[email protected]>, relay=none, delay=399463, delays=399402/0.04/60/0, dsn=4.4.1, status=deferred (connect to 192.168.1.250[192.168.1.250]:26: Connection timed out)

PHP can only say if a mail has been accepted for delivery, but not say if the mail has been successfully sent. So in both cases i got the "Message has been sent"....

So I try to find a way, to let postfix at least save the mail content (with attachments) locally on its own machine (webserver) in case the gateway isn't reachable. Because otherwise the mail, respectively the form content is gone forever.

On the other hand i already furnished a way to get an info, when the gateway is not reachable from the webserver (with the help on cronjobs). But that only helps me to notice problems faster.

Any ideas?

Thanks for helping me.

Answer 1

You need some background about the mail infrastructure. Against common belief, an e-mail is not instantaneous. The error message above (deferred) is a good example: this is a temporary failure - and in such a case, any mailsystem will try again until the queue lifetime is up (which can be a matter of days!). One example where you would see such an error is greylisting.

This means that there is no way of getting a final result at that moment of time - if you want the final result, you need to watch your inbox for bounce messages. Whenever a final error is met (for example a non-existing domain inside the To field), a bounce message from the mailer-daemon is generated - and that is your result.

Answer 2

The deferred status already means the message is queued and will be retried, by default it will attempt to deliver it for approx. 1 week. Then it will give up and send a non-delivery notification to the envelope sender.

You don't have to do anything.

You may view the queue with postqueue -p, and order it to schedule immediate delivery attempt with postqueue -i deferred.