Bouncing mail

[#1]

Quote from: Oldjim

because it was back scatter from the Plusnet servers and the function of Ironport is to sit between the servers and the outside world blocking spam etc. so that the Plusnet servers shouldn't be seeing those emails at all

Oldjim, I believe Pierre was answering my question just above his post, not yours. 

[#2]

Possibly but he then quoted my post - that is why I would like to know a bit more as I don't understand how the Plusnet servers can generate back scatter

[#3]

Quote from: Bob

The problem seems to be the amount of 'backscatter' that's originating from our relay servers. Free don't like this and have therefore blacklisted us. After a bit of investigation it's transpires that some of our mail server config's gone a bit wayward and is compounding the problem. We've a fix scheduled for this afternoon (ref: 113518) so hopefully we'll be off the blacklists before too long...

you had better tell Bob then jim

[#4]

Hi Jim,
The spam is rejected but all the bounce messages generated as a result of it are genuine and it's these that are causing the issues. We're due to be replacing the outbound email platform in the near future though which should address this.

[#5]

Matt,
Does this mean that there are two different spam blocking actions - edge protection from Ironport which rejects a very high percentage of spam without a bounce message and secondary protection taken from the spam rating which rejects at server level with a bounce message.
Alternatively does Ironport generate a bounce message but shows it as having originated from the Plusnet servers as, if I remember correctly, the outbound mail also goes via Ironport now.

[#6]

Bear in mind that not everybody has spam protection turned on, and that some spam does get through in spite of the ironport protection. I suspect this will be a major contributor but will ask Bob to clarify shortly.

[#7]

Right, here's the situation AIUI:
Messages are sent from free.fr addresses (by spammers?) using our relays. Many of these emails go to non-existent addresses or to servers that reject the message for one reason or another. This generates a genuine bounce that is then sent back to the relay servers. The relay servers will try sending this back to the free.fr address. It's these bounced messages that cause us to get blacklisted.
Historically we have never generated these bounces for domains that are not hosted by our systems. On this occasion though the bounces were getting sent due to a config error. We've corrected this error which has resolved the problem.
At the moment, outbound email goes:
Customer > Relays > Outbound IronPorts > Recipient
Soon it will go:
Customer > OutMX platform > Recipient
We'll be getting rid of the outbound IronPorts and replacing them with an in house solution that will eventually automate the process of restricting spammer's access to the servers.

[#8]

Thank you Bob - very clear

[#9]

I've checked on the blacklist today and we are still not listed so I'm closing the problem off on our end.
Matt (Networks)