Postfix DSN code explanation

Question

Since few days ago I was unable to receive automatic emals sent from my PHP application.

When I use Terminal to send an email to my @gmail address, everything works. When I try to send it to my corporate mail box, nothing happens. I looked over /var/log/mailog and found this:

Dec 21 23:14:09 CentOS-60-32-minimal postfix/smtpd[27720]: connect from localhost[127.0.0.1]
Dec 21 23:14:09 CentOS-60-32-minimal postfix/smtpd[27720]: C6E87442004: client=localhost[127.0.0.1]
Dec 21 23:14:09 CentOS-60-32-minimal postfix/cleanup[27724]: C6E87442004: message-id=<69a704388b33c4de718cef9988ea43d1@XXXXXXXXXXX>
Dec 21 23:14:09 CentOS-60-32-minimal postfix/qmgr[14698]: C6E87442004: from=<[email protected]>, size=1154, nrcpt=1 (queue active)
Dec 21 23:14:09 CentOS-60-32-minimal postfix/smtpd[27720]: disconnect from localhost[127.0.0.1]
Dec 21 23:14:09 CentOS-60-32-minimal postfix/smtp[27725]: C6E87442004: enabling PIX workarounds: disable_esmtp delay_dotcrlf for smtp1.XXXXXXXX[XXXXXXXX]:25
Dec 21 23:14:10 CentOS-60-32-minimal postfix/smtp[27725]: C6E87442004: to=<XXXXXXXXXXXXXX>, relay=smtp1.XXXXX[213.149.113.69]:25, delay=0.6, delays=0.06/0.03/0.14/0.37, dsn=2.6.0, status=sent (250 2.6.0 <69a704388b33c4de718cef9988ea43d1@XXXXXXXXXX> Queued mail for delivery)
Dec 21 23:14:10 CentOS-60-32-minimal postfix/qmgr[14698]: C6E87442004: removed

When I try to send email to @gmail address the DSN has value of 2.0.0, but when I put my dorporate e-mail address it says 2.6.0. Can someone please give some explanation on this? I have searched the google but as far as I see it there is a very little info on DSN codes.

Corporate mailbox is Exchange server, if that means anything. I have a theory that corporate mail server is somehow blocking emails from my domain, however, I have contacted the admin and he said that no blacklists have been enforced on Exchange server there.

Does anybody have some clue what is going on here?

Solution

When I try to send email to @gmail address the DSN has value of 2.0.0, but when I put my dorporate e-mail address it says 2.6.0.

2.x.x is a successful delivery, so your email is being accepted and queued for delivery by the remote mail server.

Can someone please give some explanation on this? I have a theory that corporate mail server is somehow blocking emails from my domain, however, I have contacted the admin and he said that no blacklists have been enforced on Exchange server there.

Unless custom DSNs are being sent back that aren't truthful, you're not being blocked by the mail server, but your message is in a delivery queue, spam queue or someone's spam folder. It's most certainly being accepted by the remote SMTP server (once again, unless there are some really silly things being done with DSN responses, which is highly unlikely). You need to get the mail admins on the receiving side to look through their mail logs and use message tracking to figure out what's going on with it.

Comments

[Jovan Perovic]

Thanks a lot Wesley :) At least you assuremr me that this response is expected one. I might be able to sit and talk with the admin tomorrow in order to find out what is going on here.