550 error for valid address

[#1]

Over the past few days I've been unable to send messages to a couple of email lists yet receiving messages from them. Emails elsewhere are fine.
Here's the error message:
The rejected e-mail address was '[valid list]@NETPALS.LSOFT.COM'. Subject 'Test', Account: '[valid account]', Server: 'relay.plus.net', Protocol: SMTP, Server Response: '550 <[valid list]@netpals.lsoft.com> recipient rejected - domain has no delivery address (DNS MX record)', Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79
Other subscribers are still able to send to the lists and I can logon to send direct from the netpals site.
Any ideas ?

[#2]

The error message says netpals.lsoft.com does not have any DNS MX (mail exchange) records and a check using a DNS other than Plusnet's and DIG confirms that. That means the post cannot be delivered as the error message says.
Are you sure you are using the correct address? Are those subscribers able to send using a different one?

[#3]

It's the same email addresses (2 separate lists) I've used for years and they haven't changed.
It makes no difference whether I reply to a message sent by someone else today or create a fresh message using the email address from my contacts.

[#4]

I can't see how you can use a group list hosted somewhere else using a email client on you PC going through Plusnet. Are you sure that you have done this before as from what information I can get from lsoft it seem to be around their web interface.

[#5]

Aren't some lists configured to accept posts by email? Presumably has to come from a subscribed address.
How long ago is it since you last submitted a contribution by email - more than a month? Wondering if this problem is associated with the introduction of the Cloudmark appliances in the outbound mail path.

[#6]

Yes, you have to be subscribed and most people post by email. I've been subscribed for years and any problems in the past have affected all users.
I've emailed someone else who uses plusnet to see if they're having the same problem but not sure how often they check their emails.
Last time I successfully posted was 16th Nov and first failed on 29th Nov.

[#7]

Quote from: spraxyt

Aren't some lists configured to accept posts by email? Presumably has to come from a subscribed address.

So if the list is hosted remotely are we back to the fact that NETPALS.LSOFT.COM has no MX record?

[#8]

Quote from: itsme

So if the list is hosted remotely are we back to the fact that NETPALS.LSOFT.COM has no MX record?

Yes, but lsoft.com has. I was wondering if the Plusnet relay servers should recurse into the DNS and use those, leaving resolving the subdomain to lsoft.com. Something for Plusnet to take a look at on Monday I think.

[#9]

Did a port scan on NETPALS.LSOFT.COM and it's accepting SMTP traffic so try replacing NETPALS.LSOFT.COM with 209.119.0.16
My email server will try the A record for domain if no MX record exist so perhaps PN has stop this!!!

[#10]

Me too - with a freeserve.co.uk address.

Quote

The following recipient(s) could not be reached:       'xxxxx xxxx' on 03/12/2011 15:21             550 <xxxxx@xxxxx.freeserve.co.uk> recipient rejected - domain has no delivery address (DNS MX record)

Sent it OK using Gmail instead.
There must be a problem with Force9/Plusnet's dns mx records.
Tony

[#11]

@Tony W your problem is not related to the OP, can't comment why you saw the no MX record but when checking the OP problem PN DNS servers are not used and there are no MX records

[#12]

@itsme - I will take your word for it. The phrase in the OP's error message "recipient rejected - domain has no delivery address (DNS MX record)" looked very familiar.
As I said before - sending via Gmail worked and via PN didn't, so I thought the circumstances were related. My mistake.
Tony

[#13]

I use http://www.mxtoolbox.com/ which return the actual record i.e for PN it will be mx.avasin.plus.net as well as the IP address

[#14]

I don't want to hijack this topic if my experience is actually not related.
@itsme - Thanks for the link. When I put the proper freeserve address in to that web page, it gives me a host name for freeserve and an IP address.
Why then was mine rejected before?
Tony

[#15]

Had this through from Netpals:
'Indeed there is no MX record for netpals.lsoft.com but there is certainly an A record.  The above mail server is not behaving correctly.  If a destination domain does not have an MX record, the sending mail server is supposed to fall back and try the A record.  This is per Internet standards for SMTP email.  It seems the above mail server is not doing that.'
So looks like plusnet has some sorting out to do.