DA User control of blacklists

[jkirker]

Hey all...

This is probably a silly idea but I'm curious how difficult (if not impossible) would it be in the DA user control panel to provide the users with a list of email blacklists and then allow them to select which ones their mail would be filtered by?

I have some users who want to use every available means to stop their spam and others who are comfortable with their mail client doing the bulk of the work.

Would something like this be possible? Either built into DA or as a plugin?

I do understand that exim is a completely separate function but don't understand the limitations of its config and customization possibilities.

Thanks,
John

 

[zEitEr]

Hello John,

As far as I understand it, the filtering with so called RBL is done much more before then SMTP server gets information about email itself. The filtering is based on IP reputation, thus in the current and default configuration exim declines a connection from poor IPs even without knowing for whom the email is. Your way is possible I'd rather say, with SpamAssassin+RBL (https://wiki.apache.org/spamassassin/DnsBlocklists)

 

[nobaloney]

@John,

Technically it's possible. To do it would slow down receipt of mail.

Alex is correct as far as he goes, but if you look at exim.conf you notice we don't check against blocklists until after we know both the sender and the recipient. Even though we block on IP# reputation, we don't do it until after we know who the mail is from, and who it's going to.

Why? When I wrote SpamBlocker the best practice was considered to be to not give the sending server much information as to why he was being blocked. So we waitedl until we know the IP#, the sender, and the recipient.

So we have the information.

Here's the problem: Once we have the domain name of the recipient we then need to look it up against all users to see which user owns that domain.

Once we know the user we need to look up a list kept for the users, to see which blocklists he wants to use, and then when we check the blocklists we need to look up a list of blocklists to see which users are okay with which blocklists. We could use one MySQL with multiple keys to do this except that DirectAdmin is sql-server independent, so we really can't. So we need to manipulate a bunch of separate text files every time any changes are made, and we need to search additional files every time an email is received. Instead of the way we do it now

deny message = Email blocked by $dnslist_domain
hosts = !+relay_hosts
domains = +use_rbl_domains
domains = !+skip_rbl_domains
!authenticated = *
dnslists = \
cbl.abuseat.org : \
bl.spamcop.net : \
b.barracudacentral.org : \
zen.spamhaus.org : \
hostkarma.junkemailfilter.com=127.0.0.2 : \
combined.rbl.msrbl.net[/code]
We'd need a separate stanza for each blocklist.

I've actully given some though to this; I'm in the midst of scoping out an Enterprise Email system which would offer the feature.

In fact I'd like to see personal blocklists and whitelists which users (if not email recipients) could place specific domains/IP#s/email addresses,servers.

But for a shared hosting environment I'm not sure how badly I want to do this. Unless users reallyunderstand what these lists are and how they work this would result in a lot of added technical support load.

Could something else be done? Yes. As you've likely noticed there's currently a way to exclude/include users into using the blocklists at all. A reseller or user interface could be written for that, which would be a bit easier to do. Should it be done? I'm not sure.

Years ago two people came out with plugins to manage the blocklists. Neither got any tradtion, and as blocklists were changed, both were eventually abandoned.

I recommend that people add the blocklists to the list of files which can be edited from DirectAdmin's admin level login, and for installations I do for clients, I'll always ask if they want it.

Further than that... well I'm just not sure.

Call or email me to discuss this further.



Jeff

 

[jkirker]

Thanks for the reply guys. Busy last couple of weeks with baby showers. Jeff, I'll buzz you today or tomorrow. Thanks!