When Spamfilter receive a message and the sender is like USER@LEVEL3.LEVEL2.COM  and LEVEL3.LEVEL2.COM is non in MX record, the message is rejected. This is correct .

BUT more legittimate sender have a 3'level domain also if they are not in DNS RECORD, and this gererate many false positive.

Is better if SF look for "only the presence of the 2' level domain" i.e. LEVEL2.COM

Wath do you mean ??

All you expalin is correct and i share 100% your opinion.

But there are many  "legittimate" mailing list that SEND (and only SEND) messages from an SMTP in  a server that has the name LEVEL3.LEVEL2.COM because it is in a domain LEVEL2.COM, but this is not the fully qualified MAIL server of the domain.

For this matter i was thinking that, problably, is better to check only if the domain LEVEL2.COM in existent or to check if server LEVEL3.LEVEL2.COm is existent at bDNS level and not to MX record level.

Compliments for your work that i, really, think is excellent.

Yes... I had the same problem... A ListServ for a major client of mine used a third level domain and everything was rejected because there was no MX record for the third level.

I just added them to the white list and all seems well.   It was very annoying because my client refused to acknowledge the need of a valid MX record.

The problem with SpamFilter logic is that an MX record is NOT required in order for an email address to be valid and deliverable.

-Matt

Please show us where and by whom it is documented to be a *good* or *suggested* practice to prevent spam.  Furthermore and more importantly, show us where and by whom it is stated that SMTP servers requiring an MX record for the "domain" should ignore normal domain lookup rules.

Actually, ignoring the logical definition of a domain for the purpose of this feature is the original issue that I complained about and the only complaint I've read from anyone because it causes massive false positives.  It is interesting to note that early versions of SpamFilter SPF had the same problem.  Fortunately, logic prevailed or that too would have been a useless feature as this MX filtering feature is in its current state. 

SpamFilter does a tremendous service by offering logical means of filtering email. Offering illogical means of filtering email serves the chosen few that understand and want such a feature.  All along everyone's problems with this feature have been the illogical application of a logical idea.

I would be happy if the feature were at least not so misleading by labeling it appropriately, ie "Require All Hostnames have a MX Record".   You would not get so many questions about this if the feature was labeled appropriately.

I am willing to bet that all users would like to have a logical version of this feature that, just like SPF, is based on the actual domain and not assume every A record is a subdomain.

Heck, your half way there now, relabel the existing feature appropriately and add the ability to require MX records in the actual domain.

-Matt

Roberto,

You've put a lot of hard work into this product so I really hate to disagree with you, but I do.  The first two references you quote support what I have saying and treat domains as domains and A records as A records.  The third reference is not relavant because it's an article by someone in 2003 that is suggesting we do something like require an MX record for every sending server, which is not what your intensions were.  There is nobody that supports your notion of some special non-standard "email domain".  All of the articles I've implement an MX checking feature in the proper way which is to not assume an A record is a domain.  This is the only feature that SpamFilter contains that does not follow common practices.  It's your baby.  I'm sure you'll continue to hear from frustrated users that were confused by the current implementation.

The good news is SpamFilter does the job better than any other product available! I still love it!

-Matt (da bratt)