Additional AntiSpam Methods

Support General Configuration
1

Hello,
As part of the AntiSpam policy, I use the following options:
(a) BlackList (blocked email addresses)
(b) DNSBL (DNS BlackList)
(c) DNS Check
Reject message if originator’s domain has no MX entry – only
(without option ‘Reject message if the originating IP has no reverse DNS entry’)

In the logs (smtp_in.txt) I can see that methods A and B are working properly, if they occur, the mails are rejected, regardless of whether method A or B occurs alone or together
Part logs for method A:
Set smtp action to REJECT
Set smtp explanation to [Your email address is blacklisted]
and similarly for the method B:
Set smtp action to REJECT
Set smtp explanation to [DNSBL record found]

Unfortunately, method C, when it occurs alone or with the others (method A and/or B), does not work properly (despite the condition no DNS MX), mail is accepted
I see such entries in the logs:
Set smtp action to REJECT
Set smtp explanation to [Sender domain <xxxxxxx.yyy> has no DNS MX entry]
But the mail is received, what could be the reason for this behavior?

Some of the logs of the described case:
(…)
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: MX validity failed for <xxxxxxxxx.yyy>
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp action to REJECT
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp explanation to [Sender domain <xxxxxxxxx.yyy> has no DNS MX entry]
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp action to REJECT
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp explanation to [DNSBL record found]
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp action to REJECT
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp explanation to [DNSBL record found]
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp action to REJECT
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp explanation to [Your email address is blacklisted]
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set local delivery to all
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp action to ACCEPT
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Clear smtp explanation
(…)

Best regards
bcteam

2

Hello @bcteam

Could you please provide the smtpFilters.script and a fresh new SMTP-IN session (before this please configure SMTP Receiving service log level to Protocol Communication) so we have all needed data?

From above I see:

02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set local delivery to all
02-01 22:58:37 +0100 08 server1 SMTP-IN:00011892: Set smtp action to ACCEPT

but I have no idea why the action was set to ACCEPT the message instead of keeping the REJECT decission (based on DNS check and presence into DNSBL).

HTH,
Ioan

3

Hi

@indreias - thx for your answer.

The primary problem was solved, I checked the active smtp filters (smtpFilters.script) again and found an error, I corrected it and everything works fine.

I have one more additional question about the MX record in the smtp log (smtp_in.txt), I can see three types of messages:
(a) MX validity verified for <email1@A-example.xxx>
(b) Unable to determine MX associated with <email2@B-example.xxx>
(c) MX validity failed for <email3@C-example.xxx>

message “a” - all right
messages “b” and “c” - indicate that the MX record could not be identified.
What is the difference between the “b” and “c” messages, ie what results in “b” or “c” message
and/or what condition was not met with these validity?

regards,
bcteam

4

Hello @bcteam

Please increase DNR service log level to Protocol Communication and check DNR specific log lines for the differences between (b) and (c).

As I have no access to the code right now :innocent: I could imagine that (b) is for domains that are returning timeout or SERVFAIL answers when the MX record is requested and (c) is for domains that have no MX record(s).

I have no samples at hand for these 2 cases so I could not double check above supositions - if you do not mind to share some examples I could provide better explanations.

HTH,
Ioan