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Luca
Newbie
Joined: 15 October 2006
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Posts: 17
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| Posted: 10 May 2007 at 11:33am | IP Logged
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Hello,
in a multipart message, the part boundaries format used by MailBee seems to trigger most common antispam filters. As a result, messages constructed with MailBee (independently of which component is sending them) generate high spam scores and are generally filtered out.
The spam rule which is triggered is:
MIME_BOUND_NEXTPART Spam tool pattern in MIME boundary
You can reproduce this issue by checking any MailBee-generated multipart message with SpamAssassin32:
http://sawin32.sourceforge.net/
(I've tried manually changing part boundaries in one message's raw body, and substituting them with boundaries similar to those produced by Outlook, and it fixes the problem for that message)
The problem occurs with a lot of very popular antispam filters (both server-side, as Spam Assassin, and client-side, as AVG) - if you are using your own components for sending out your newsletter, this may be very relevant for you too ;-)
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Alex
AfterLogic Support
Joined: 19 November 2003
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Posts: 2206
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| Posted: 10 May 2007 at 1:58pm | IP Logged
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We tried http://sawin32.sourceforge.net/ to check what's going on there but could not make it work. I submitted MailBee message and got MIME_BOUND_NEXTPART in X-Spam-Status. Then, I manually took the boundary from a SPAM mail and then pasted it into MailBee message instead of the original one. MIME_BOUND_NEXTPART disappeared! Looks quite strange that SPAM mails receive less score.
I think there is some kind of a bug in SA rules.
Regards,
Alex
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Luca
Newbie
Joined: 15 October 2006
Online Status: Offline
Posts: 17
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| Posted: 10 May 2007 at 8:14pm | IP Logged
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Hi Alex,
I agree with you with that - I mean, that it's SA fault, not MailBee; and a rule based on boundaries is silly in itself if you ask me.
But the problem is that Spam Assassin engine is the most widely used on the Internet by far: apart from the server side versions, which run on most Linux mail servers, it is incorporated in a lot of commercial software too (as AVG security suite) - see http://spamassassin.apache.org/
As a result, messages created with MailBee encounter great difficulties in being delivered - we were first alerted about that by a lot of users (we publish a mailing software), then that was checked by us and confirmed.
I see two possible workarounds: either the dll is updated so that boundaries can be somehow changed, or some code could be provided that works on raw body and changes boundaries without breaking the message structure.
I know this is bothering, as it comes from someone else's poor design... but there's no other option as it is impossible that mailservers worldwide update :)
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Alex
AfterLogic Support
Joined: 19 November 2003
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Posts: 2206
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| Posted: 11 May 2007 at 12:41pm | IP Logged
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You know, we contacted SA support, they said that MIME_BOUND_NEXTPART should not really cause the message to be considered spam. It's score is just 0.2 while 6.3 is required to consider a message to be spam. Maybe, there is something more important in that mails which were filtered out? Could you submit the entire X-Spam-Status string of a typical message which gets blocked?
I think we'll anyway make boundaries SA-safe but I'm not sure it will really help in your case (if you're getting high scores for some other reason).
Regards,
Alex
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Alex
AfterLogic Support
Joined: 19 November 2003
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Posts: 2206
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| Posted: 11 May 2007 at 4:00pm | IP Logged
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http://www.afterlogic.com/updates/mailbee.zip is MailBee.dll with fixed boundaries. This should decrease spam score by 0.2.
However, we're still interested in what makes e-mails you're sending get spam level score.
Regards,
Alex
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Luca
Newbie
Joined: 15 October 2006
Online Status: Offline
Posts: 17
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| Posted: 12 May 2007 at 4:39am | IP Logged
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Hi Alex,
thank you, that was great as usual!
The rest of the spam issue does not involve Mailbee objects at all; it comes from the way messages are composed - using "too graphic" e-mail templates, so that rules like these are triggered:
HTML_IMAGE_RATIO_04
DC_IMG_TEXT_RATIO
But this is something I can easily deal with (it's just a matter of designing better templates).
SpamAssassin allows changing rules' scores and spam thresholds, and I've noticed that a lot of servers use 4 (instead of 6.3) as a spam indicator - while some softwares use higher spam scoring for each rule. Therefore, even small improvements may make a big difference.
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Alex
AfterLogic Support
Joined: 19 November 2003
Online Status: Offline
Posts: 2206
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| Posted: 12 May 2007 at 7:46am | IP Logged
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Yes, this makes sense. Thank you for your feedback.
Regards,
Alex
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