Blocked by Hotmail? Use a Microsoft mail client instead.
June 20th, 2007
After being told that “SmartScreen technology” had blocked his server from sending mail to Hotmail, this guy found that if he used Outlook 2003, rather than Thunderbird, he could get his mail delivered. Not that you should be surprised by that. It’s not like Microsoft client headers appear in a whole lot more spam than Mozilla headers. Oh wait a second, Microsoft headers do appear in at least half of all spam.
http://www.theregister.co.uk/2007/06/15/spam_nothotmail/page2.html
“I started playing around with clients rather than concentrating on server setup, and I’ve had some interesting results. I can send to Hotmail without a problem using Outlook 2003, but no cigar with Mozilla Thunderbird. I think that this suggests that the headers the email clients add to an email also play a crucial role in determining if the mail gets through or not. This is BAD news because as a system admin there is generally very little you can do about this.”
Entry Filed under: Email, Technology
2 Comments Add your own
1. spenser | July 17th, 2007 at 6:46 am
From my experience, this has more to do with the fact that the mozilla derived clients all use ip address literals in the smtp handshake instead of something like localhost.
For example, outlook express properly gets authenticated when relaying through mdaemon and netscape 7.2 does not. Mdaemon rejects the session before getting to sender authentication based on the presence of the address literals in the initial handshake. Of course, being behind a NAT, the address literals are of no use at all, and do not match the translated address.
A search of usenet turns up a myriad of complaints about this going back several years. The developers say it’s rfc compliant, so go away. The fact that it trips over many email servers cuts no ice with them.
2. dos | July 18th, 2007 at 2:39 am
As an anti-spam software developer I tend to disagree that the client presenting an address literal (which is properly enclosed in square brackets) in its helo to its own MSA should have any effect on whether a remote system (that the client doesn’t directly talk to) should or should not accept the message.
The fact that NATing causes the IP to be different from the publicly visible IP isn’t a problem. That’s the whole point of address literals… for when the client has no idea what its hostname is. An address literal, even of a private IP, is a lot more accurate than something like “localhost” or “joespc”.
Of course it’s quite possible that Microsoft in all their wisdom is targeting address literals in the initial (MSA) received header field value. IMHO that’s a pretty brain dead way to operate though.
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