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email 'To: header truncation using PlusNet anti-spam/virus

N/A

email 'To: header truncation using PlusNet anti-spam/virus

Since PlusNet announced the upgrade of their anti-spam and anti-virus services some weeks ago, we have consistently experienced a problem where the 'To:' header is truncated at around 1,000 characters, preventing delivery to recipients whose address is beyond the 1,000th character of the list.

We have carried out extensive tests that lead us to the conclusion that the PlusNet servers or anti-spam/anti-virus services may be at fault.

I have reported the problem through a 'Contact Us' ticket and am awaiting further action, but I would be interested to hear if any other PlusNet users have experienced similar problems.

Obviously this only affects messages which have large circulation lists - typically forty or more recipients - but it does prevent the email from being routed to the correct recipients. It also means that these emails fail to comply with the relevant RFCs.
4 REPLIES
jberry
Grafter
Posts: 1,886
Registered: 08-06-2007

email 'To: header truncation using PlusNet anti-spam/virus

Hi there,

If this problem only affects you when you are sending to multiple recipients as well as this issue (which I have now sent back to the networks dept who will pick it up on Monday) you will also see a significant slowdown because of TarPitting. Could you not set up some mailing list software instead? This will fix your problem and speed it up.

Obviously we will look at the problem as well to see if this can be resolved.

Regards,
jberry
Grafter
Posts: 1,886
Registered: 08-06-2007

email 'To: header truncation using PlusNet anti-spam/virus

Hi there,

I am not able to replcate this (with 20 addresseess usiong very long aliases so that it is >1000 charactors. Have you tried sending them as text rather than HTML .. does this make any difference?

We do want to get to the bottom of this problem but unless we can replicate it here there is nothing we can do really. I am using OE. What client are you having problems with?

Regards,
N/A

email 'To: header truncation using PlusNet anti-spam/virus

Josh,

This only appears to affect incoming email traffic that has long 'To:' headers, when it passes through PlusNet's new spam/virus filters. Due to truncation we are often unable to determine the appropriate recipient at our end.

We can send out emails via relay.plus.com (which do not pass through PlusNet's spam/virus filters) with long headers and they will arrive at non-PlusNet subscribers wholly intact.

Further tests, using the same client on our end, show that:

1/ We can send out emails via relay.plus.net with long headers and they will arrive intact at PlusNet subscribers who do NOT have PlusNet spam/virus filters activated.

2/ We can receive emails with long headers via our other ISP's pop3 server without truncation.

3/ Emails received by us, via mail,plus,net, through the PlusNet spam/virus filters, from users of other ISPs, have truncated headers.

Incidentally, I have not tested long CC: and BCC: headers, but there is a good chance that they will suffer in the same way.

Is the new spam/virus filtering software authored in-house by PlusNet, or is it an outsourced product? I suspect that an abitrary choice of 1000 bytes has been made somewhere for the size of the header buffers.
jberry
Grafter
Posts: 1,886
Registered: 08-06-2007

email 'To: header truncation using PlusNet anti-spam/virus

Hi there,

I have sent myself a mail, to an account with AV turned on, with well over 1000 charactors in the to field and it came through with no problems and no truncation. The only difference I could see is that mine was sent plain text and the example in your ticket was HTML - so we are not able to replicate it on the information you have given me.

The software is open source pagages modified to our requirements (although they are heavily modified since no exisiting open source spam package we could find scaled up to what we needed on its own).

Regards,