Hello everybody. Sorry my first post here is a request for information, but I'm going crazy trying to solve a problem with postfix and have run out of ideas. For information, the FQDN of my site is luna.lowcarbon.com. I've followed all the instructions here:

http://library.linode.com/email/postfix ... -6-squeeze

but, when I send email from my site (e.g., when my mediawiki installation tries to send login details to users), I get the following in /var/log/mail.log:

May 1 18:21:13 luna postfix/smtp[27187]: 5B8C07404E: to=<PERSON@SOMEDOMAIN.com>, relay=SOMEDOMAIN.com[91.103.217.17]:25, delay=0.07, delays=0/0.01/0.03/0.02, dsn=5.0.0, status=bounced (host SOMEDOMAIN.com[91.103.217.17] said: 550-Verification failed for <www-data@luna.lowcarbonuk.com> 550-The mail server could not deliver mail to www-data@luna.lowcarbonuk.com. The account or domain may not exist, they may be blacklisted, or missing the proper dns entries. 550 Sender verify failed (in reply to RCPT TO command))

So it seems the site I'm sending to tries to ping back to see if the sender (www-data@luna.lowcarbonuk.com) exists, presumably as an anti-spam measure. Using the instructions in the Linode link above, I think I have created a mail user in MySQL called www-data@luna.lowcarbonuk.com (they're certainly visible in /home/vmail/luna.lowcarbonuk.com/www-data) but this hasn't solved the problem.

If anybody has any advice on what I might do now I'd be really grateful as I'm tearing my hair out!

Lowcarbon.com is in DNS but luna.lowcarbon.com is missing.

Thanks, vickd. DNS is something I've only limited experience with. I have an entry for luna.lowcarbonuk.com in the MX records and there's an entry for 'luna' in the A records. Can you please give me any idea of what should be in the DNS?

Nope, nothing for luna.lowcarbon.com, MX apparently set to an external email host.

Retrieving DNS records for lowcarbon.com...

DNS servers
c.ns.bytemark.co.uk [80.68.80.27]
b.ns.bytemark.co.uk [85.17.170.78]
a.ns.bytemark.co.uk [80.68.80.26]

Answer records
lowcarbon.com      SOA   
server:   a.ns.bytemark.co.uk
email:   hostmaster@lowcarbon.com
serial:   1335906745
refresh:   16384
retry:   2048
expire:   1048576
minimum ttl:   2560
   2560s
lowcarbon.com      NS   a.ns.bytemark.co.uk   259200s
lowcarbon.com      NS   b.ns.bytemark.co.uk   259200s
lowcarbon.com      NS   c.ns.bytemark.co.uk   259200s
lowcarbon.com      TXT   MS=ms71592886   3600s
lowcarbon.com      TXT   v=spf1 include   86400s
lowcarbon.com      MX   
preference:   10
exchange:   www-lowcarbon-com.mail.eo.outlook.com
   86400s
lowcarbon.com      A   50.57.155.185   86400s

Authority records

Additional records
a.ns.bytemark.co.uk      A   80.68.80.26   86400s
a.ns.bytemark.co.uk      A   80.68.80.26   86400s
b.ns.bytemark.co.uk      A   85.17.170.78   86400s
c.ns.bytemark.co.uk      A   80.68.80.27   86400s
c.ns.bytemark.co.uk      A   80.68.80.27   86400

Retrieving DNS records for luna.lowcarbon.com...
Attempt to get a DNS server for luna.lowcarbon.com failed: luna.lowcarbon.com does not exist in the DNS

Did you use the Linode DNS manager or the bytemark DNS? As bytemark name servers are used for the domain you have to do it there.

In your question, you use the domain 'lowcarbon.com'; in your logs and examples, you use 'lowcarbonuk.com'. The DNS for 'lowcarbonuk.com' looks OK to me and I appear to be able to send mails to your test userid (www-data@luna.lowcarbonuk.com).

_________________
/ Peter

Thank you everybody. I'm feeling extremely stupid: I did indeed type lowcarbon.com in my question when I meant lowcarbonuk.com.

Thank you to everybody who replied and tested the email address in question. It's now working fine for me too; I think the issue must have been the DNS records not having propagated.