We send mail to your mailserver from mail.intermodulair.nl
Than we get "450 ns1.intermodulair.nl(62.58.53.110) client host rejected service is unavailble"
Please advice.
Rik
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GreenNet provides a unique anti-spam service geared to NGOs, the voluntary sector, charities and activists.
GreenNet, Development House, 56-64 Leonard Street, London EC2A 4LT.
Tel (UK): 0845 055 4011 Tel (int'l): +44 (0)20 7065 0935 Fax: +44 (0)20 7065 0936.
Email: info@gn.apc.org Twitter:@GreenNetISP
Contact GreenNet
Please note that the opinions of our user community do not necessarily reflect the opinions of the GreenNet Collective.
Comments
Re: your mailserver reject mail
Hi,
this is due to greylisting (http://projects.puremagic.com/greylisting/) - a new antispam measure. As it's going to be implemented on many mail servers soon, our advice is to fix your end - make sure that the mail daemon mail.intermodulair.nl complies with RFC 821, APPENDIX E, response to the 4yz code (http://www.pku.edu.cn/academic/research/computer-center/tc/html/RFC821.html).
Best
GreenNet Support
Re: your mailserver reject mail
What are we supposed to do when we send e-mail to friends and family at gn.apc.org and it is rejected and sent back to us? I can receive e-mail from one of your customers, but when I reply to him, you reject it. This is very frustrating.
Re: your mailserver reject mail
If you have problems contacting any addresses on GreenNet, please
1) For urgent messages or if you get a bounce, you may want to send the message again. By this time your message will be cleanlisted and the second message should go through immediately.
2) Ask your ISP to check their server(s) for retry times in response to a 450 message. There are known to be two buggy mail server programs which do not comply with internet standards, [url=http://lists.puremagic.com/pipermail/greylist-users/2003-July/000117.html]Novell GroupWise 6.0[/url] and [url=http://www.rhyolite.com/pipermail/dcc/2004/002059.html]InterMail 4.0[/url]: please let your ISP know that if they still use one of these, emailling will be unreliable to an increasing number of other ISPs. Alternatively, it could be a misconfigured version of Exim.
3) Contact GreenNet by phone or email, giving the sender and recipient addresses and the date the email was sent or rejected through the other ISP. We can then investigate and if necessary, add the mail servers to our cleanlist.
Post Edited (07-08-04 09:47)
Spam - and nonspam -filtering
As a long-time supporter of GreenNet (I knew Mitra!) I have to say that I don't think it's good enough for Greennet to use spam filtering which results in non-spam messages being rejected, and then to say that it's for others to fix their servers. I have experienced important messages being rejected, and this creates serious problems especially when one doesn't know that one was supposed to have received a message at all. Further, the delays caused by messages being rejected - even when they do eventually get through - seem to me at times to be serious, and to cause considerable problems. I think this filtering is ahead of its time, and GN should consider dropping it, encouraging all of us to set up our own filters, and coming back to it when the world out there has caught up. Certainly, I shall have to switch ISPs if the current situation continues - something I'd hate to do as I have the highest regard for GreenNet and the work that it does, and especially for the support staff who are always very helpful. But I simply can't risk this sort of thing happening repeatedly.
Re: Spam - and nonspam -filtering
Email has, contrary to popular belief, never been either instantaneous or perfectly reliable. For example, a mail gateway that's run out of storage may result in the non-delivery of a message not being reported for 5 days. It's difficult not to have any anti-spam system nowadays, and each has to prioritise absence of false positives over false negatives. Manual deletion makes mistakes too, and on balance we've had very positive feedback about the success rate of greylisting, when combined with SpamAssassin and SpamCop queries. The delay in accepting unrecognised email allows its status to be confirmed one way or another.
We are of course encouraging the rest of the world (except the spammers!) to catch up. Some sysadmins respond immediately by patching or upgrading their software, while other cases (including one large ISP) are aware they have hard-to-fix problems, we cleanlist the servers, but their users may still have problems elsewhere.
If somebody is taking responsibility for their own spam deletion we can turn off greylisting for a particular recipient address or addresses, and it looks like that's most appropriate here.
Re: your mailserver reject mail
GreenNet's greylisting system was greatly improved earlier in 2005 to minimise any delay in receiving genuine email from unknown sources. There are now only a very small number of providers that may still have problems forwarding email to GreenNet - we have found two district councils using obsolete software, and one ISP in West Africa. In each case we find, we cleanlist the problematic server as well as notifying its owner of the problem which is exposed not just by greylisting, but under a number of other possible situations.
The history of the most problematic broken software is complicated. InterMail was apparently called InterMail Post.Office at version 3. Possibly because other factors were involved, it appears the bug was not addressed until late in version 4. The rights for this were later sold from Openwave to Tenon [url]http://www.digitalpoint.com/lists/59168.html[/url].
There is no evidence the bug is in any software published since 2001, but migration from the obsolete proprietary software is difficult: [url]http://archives.neohapsis.com/archives/postfix/2002-07/2455.html[/url] . This is apparently why it is still in use in some places and dropping emails.
Greylisting more widely adopted
Yahoo! now greylists much of its incoming mail... see http://mostlyexchange.blogspot.com/2006/12/yahoo-is-getting-serious-abou... - this seems to be causing problems with buggy email servers. RFC2821 is quite clear, and Yahoo is in the right and NTL is wrong.