I have postfix running on my debian linode, and I have a number of scripts that will send an email to the user from PHP (i.e. forgotten usernames, what have you).

For ~30-40% of my users, these messages arrive without fail (gmail.com, hotmail.com users). But for others, like aol, comcast, etc, no email ever arrives.

Looking through my mail logs, I see the following:

host mailin-02.mx.aol.com[205.188.155.89] said: 550 REQUESTED ACTION NOT TAKEN: DNS FAILURE

This was on an attempt to send mail from my linode to aol.

UNfortunately, I am a complete newbie when it comes to properly configuring postfix. I have tried many times to configure it properly, but have clearly failed.

My server is just used for outgoing mail from php via postfix. I believe that it rejects incoming mail properly, and is not relaying at all (from probing it and reading the logs).

Can anyone help me out with this problem? I can post my postfix conf if needed.

Your help is greatly appreciated!

Have you set up reverse DNS from the Linode control panel? It may just be that those hosts require reverse DNS.

Well, I think so.

Looking at it, my IP is pointed at mydomain.com. Should it be pointed at mail.mydomain.com, as this appears to be where my mail is originating from?

Apr 29 11:46:23 localhost postfix/qmgr[531]: 3E67717447: from=<www-data@mail.mydomain.com>, size=352, nrcpt=1 (queue active)

I have added mail.mydomain.com to my zoneedit account that I use for dns for this domain, as an alias. Is ther a chance this will rectify the issue?

Also, how can I change the user the mail is being sent from?

It's hard to say without a more detailed report from the rejecting server. Here's what I found with a search:

550 Requested action not taken: DNS FAILURE
These errors indicate that there are DNS resolution problems somewhere between your domain and AOL. This usually means that AOL is unable to resolve your domain name in DNS before accepting that mail for delivery. Contact your e-mail administrator for assistance. The network administrator for the site may have to modify their resource records in DNS.

I'm not sure if you've already seen that or if it's helpful...


The user sending mail is always going to be www-data, since that's the user your PHP interpreter, apache, is running as. This is not the same as the "From" address. I don't think that this discrepancy should be part of the problem at all.

OK, am going to test a few emails to a friend on aol, will let you know of the results later today.

Thanks!

AOL has some postmaster help pages:
http://postmaster.aol.com/trouble/index.html

including a rdns tool:
http://postmaster.aol.com/tools/rdns.html

You can check/modify your Linode rdns via:
https://www.linode.com/members/rdns.cfm [requires login]


See also: http://postmaster.aol.com/tools/whitelist_guides.html

Solving it for AOL will probably solve it for all refusing MXers.


HTH,

Cliff

OK, I think I fixed it...

Postfix is sending mail from mail.mydomain.com

I did not have a CNAME entry in dns for mail.mydomain.com, so it was not properly resolving, duh!

AOL is not gladly accepting mail.

I have setup SPF on the DNS server as a TXT entry, is there anything else I need to do?

Finally, I use Gmail to send mail for my domain (i.e. correspondeance, not auto-generated mail from PHP). For my SPF entry, should I add the outgoing gmail servers as well?

Thanks for the help so far,

P

Congratulations!

As far as SPF: yes, you will need to add the gmail servers. I think this is the biggest disadvantage of SPF, that you need to think of everywhere you might possibly send mail from and put those in your DNS. As far as a solution to that, smarter men than I have failed.