Postfix Mailer Error - SMTP error code

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Postfix Mailer Error - SMTP error code

Hey there, this might not be the most appropriate place to put this post but I thought I would try to see if anyone has any suggestions or knowledge.

I am using Postfix mailer to send emails which are triggered by a php script from the web server. Most emails are being sent fine, however sometimes I am getting errors. One in peticular, #451 4.1.3 Sender address does not resolve. The other is, #450 4.7.1 Client host rejected: cannot find your reverse hostname.

I think both of these are very similar because the client side is unable to resolve my hostname. If anyone out there has any helpful information that would be very much appreciated.

Thanks!

Message was edited by: WestB

Message was edited by: WestB

Mac OS X (10.5.4)

Posted on Jul 8, 2009 8:13 AM

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Answer 1

Camelot

Level 9

58,581 points

Jul 8, 2009 9:13 AM in response to WestB

Unless you have a flaky DNS server, they are likely two different problems.

The first error:

451 4.1.3 Sender address does not resolve

indicates an error in the sender's email address - it's from a domain that does not resolve, and therefore is rejected by postfix.

The second issue relates the client's IP address:

450 4.7.1 Client host rejected: cannot find your reverse hostname

Here postfix is rejecting the message since the client's IP address doesn't resolve to a valid hostname.

Now if these errors are transient, but on the same servers then it may be your DNS server isn't resolving the sender domain and/or the client's IP address. Otherwise I'd expect these errors to occur all the time if you're sending from the same address and generating the emails on the same machine.

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Answer 2

WestB Author

Level 1

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Jul 8, 2009 10:26 AM in response to Camelot

We do not have a DNS server, this server is simply a Mac OS X machine with an old version of Apache installed on it. As for PHP and Postfix I have no idea really how they got their in the first place but they were there so I used them.

I really would love to strip the machine and install what I want on it but all of this stuff is live.

But I do have some questions in regards to what you said,

The first error:

451 4.1.3 Sender address does not resolve

indicates an error in the sender's email address - it's from a domain that does not resolve, and therefore is rejected by postfix.

So far I have sent 44 emails, 3 didn't work, giving me the errors I wrote about. If there was an issue with the email address I am sending from why would the others send and these ones not?

The second issue relates the client's IP address:

450 4.7.1 Client host rejected: cannot find your reverse hostname

Here postfix is rejecting the message since the client's IP address doesn't resolve to a valid hostname.

The error states it cannot find "your" hostname which I assume means mine, so when you say "client" are you speaking of the postfix application? Can you clarify.

Thanks for your response and assistance, hope you can continue to help me out. Appreciate it.

Ben

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Answer 3

etresoft

Level 9

56,692 points

Jul 8, 2009 11:58 AM in response to WestB

WestB wrote:
I really would love to strip the machine and install what I want on it but all of this stuff is live.

That is bad news. Really bad news.

So far I have sent 44 emails, 3 didn't work, giving me the errors I wrote about. If there was an issue with the email address I am sending from why would the others send and these ones not?

I am surprised to see that 41 worked. This means that 93% of your e-mail recipients have their servers configured incorrectly.

Now, to explain. You really can't do what you are attempting. You are trying to send mail from a machine that really isn't a server. In order to send e-mail reliably, you need a static IP address and good nameservers to map your sending domain name to your IP address. It sounds like you don't have that. If not, your messages will be identified as SPAM and, hopefully, rejected.

Your best bet is to get some sort of hosting provider to send your e-mail for you. Your machine could easily do all of that if you had it installed in a co-location environment and had all the nameserver and e-mail settings correctly matched.

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