Plusnet billing servers may have been hacked.

[#1]

Google is reporting to me that:  "We've found that lots of messages from billing02.servers.plus.net are spam", indicating that the billing servers may have been hacked.  Clearly, some messages from billing02.servers.plus.net must have been marked as spam by its recipients for this warning to have been triggered.  The question is:  how many messages marked as spam does it take to trigger the warning?  One?  One hundred?
The problem of course, is that anything issued from billing02.servers.plus.net, and going to Google addresses, is now being filtered out as spam and runs the danger of not ever being opened by its intended recipient.
If spam really is being issued from billing02.servers.plus.net, then Plusnet need to investigate.  If spam is not being issued from billing02.servers.plus.net, then Plusnet need to know that Google is diverting email communications into their recipients' spam boxes, thereby interfering with the business.
Oh, and don't think that this has happened because a single user's spam filter has changed:  it has not.  This "spam" warning has happened "out of the blue", without any user intervention.

[#2]

Hi there,
Was there a specific reference on the email? It'd help with our investigations, though I'll make sure I let our networks team know about this anyway.

[#3]

Hi...
yes, it says    Email ref: E0281
The email was my regular notification from support@plus.net of my Direct Debit Payment Details.  I have received hundreds of these notifications previously with no problem at all.  I have not instigated any changes in my googlemail spam filters. 
Besides which, Google only identified it as spam because "Why is this message in Spam? We've found that lots of messages from billing02.servers.plus.net are spam."
It is the nature of their claim which riled me.  I thought I should report it.

Cheers,
keith

[#4]

Wouldn't be at all surprised if this was down to people marking payment reminders as spam out of irritation I'm afraid, did you click the not spam link?

[#5]

Hmmm..  I can see that is a plausible explanation, although it has never happened to me before.  I will mark it as "Not Spam" now (once I do that, I lose the evidence of their message where Google claim they see a lot of spam from your servers, so I held off.  Curiously, I received that same Google claim referring to messages from the Marine Conservation Society mail server last week, too - and they just send to members.  I warned them, too.)

Cheers, and thanks.

[#6]

My direct debit and referrals discount emails went into spam as well this month - I never mark anything as spam because Google usually do a good job of filtering the junk.
I have now marked them as 'not spam' so I will see what happens next month.