Unable to send email to Plusnet domains

We are a small ISP and have suddenly in the last few weeks had a problem where customers cannot send email to PlusNet domains from our SMTP relay servers.

The relay servers are clean - not on any RBLs - PTR records in place, correct HELO etc.
Using Cisco's senderbase.org shows shows the servers reputation as 'Good'.
No problems sending to anybody else except domains hosted by Plusnet.

Phoned PlusNet to discuss the problem, hoping for a pointer and met with total disinterest - 'ask our customer to contact us'.

Has anybody else seen this - if so any clues. All has been fine until about two weeks ago. None of our relays can send mail to plus.net.

Colin

Hi Colin,

The recognised process for dealing with a situation like this is to send an explanation/supporting evidence to abuse(at)plus(dot)net

I can probably have a look for you though as the above method is likely to take some time.

If you can send one of the offending messages to a *non-Plusnet* email account and then provide me with a full copy of the received email/headers, then I should be able to work out what's going on.

Send the details via PM, rather than post here of course.

Rgds,

Bob,

Please look at ticket #113870225

John

colin if you like send me th recipient's addy in PM and I will try to send an email, if it fails I will happily pass on the raw error logs to you so it can be raised with plusnet properly or I may even raise it myself directly.

As it sounds like you dont have access to your server's email logs, which is the sort of thing plusnet will need to investigate.

It's sending specifically from the mail servers Colin runs to Plusnet. I've been helping by agreeing to be a recipient on Plusnet with a copy to my gmail account. Colin does have access to the full logs on his servers.

I reported the issue to Plusnet and their support was absolutely useless. They were absolutely adamant that the sending server would be getting a 550/552 response from the Plusnet servers and that isn't the case.

Many thanks for the offer. I have already had a couple of offers of help and bpullen and jelv have submitted headers and logs to plusnet for me.

It seems to be all our sendmail servers - and it only started about three or four weeks ago.
I have installed Synametrics SMTP gateway as a workaround and this delivers fine.

Seems very odd as sendmail and postfix are pretty much the defacto MTAs for *nix smtp servers and I would have thought others out there must be seeing issues. Plusnet aren't bouncing the messages - just timing out - so 441 errors.

I'll pick it up once I've received some further details from Colin. I was out of the office late last week.

Rgds,

Have you looked at my ticket? There's a load of extra info (including their mail server logs) on there.

Yes, I have.