Topic: Mail Filtering & Whitelists

[dave simmons]

Mail filtering (Spamassassin) is working perfectly, but I have the problem that something is stopping good mail also.  It's not in the spamassassin filtering itself, but in the rejection of DNS - in the qpsmtpd log I see "Domain has demonstrably bogus MX records" when one of my colleagues tries to send me a  mail.  I think (hope) that this refers to the sender and not to us! 

I have added the domain of the sender into the whitelist panel in the server manager - in the boxes whitelisthelo, whitelistsenders, and whitelist_from (under the format domain.be - no username or mx or www) - but the mail is still not getting through.  I want either to be able to allow all mail from this domain to get through to us or only to disactivate the bogus DNS check (and leave other protection in place if possible). 

I said earlier in the post that I hope the the comment about demonstrably bogus DNS records refers to the sender and not to us.  I find it a bit strange because the sender is in a department of a major university here in Belgium, and they have probably a whole IT department.  I would expect them not to have any problem with configuration of domain names.  He is however at a remote site (not on campus) and they have a different ISP.  Maybe this is the reason.

I have searched the documentation but can't find anything.  Can someone please give me some guidance?

[mercyh]

Dave,

I know this is late but did you ever get this sorted?

Check out the following topic:

http://forums.contribs.org/index.php?topic=40601.0

[dave simmons]

Hi, thanks for the reply.

Didn't really get it properly sorted.  Just disabled all filtering except spam filtering.  We get a few more spam mails than we did before, but we also get "good" mails which were being filtered out.  It's maybe not the perfect solution - but I prefer it to not receiving mails which I need to receive.

The danger with the blacklisting is that we don't receive some "good" mails - without realising it.  Because some mails come in, you don't realise that some are not getting through.

We only have 7 users on a dual-processor Dell Poweredge, and so it shouldn't be overworked by Spamassassin.

I recently posted a (for us) more serious e-mail problem on the Bug Tracker.  As I have receive no reply on that system, I'll re-post it here - maybe I'll get some feedback.

Here is the complete post:

There was one update to be applied in the server-manager last weekend
(29/3/08).  I don't know what the update was!

Since this weekend, our 3 users who work from outside the office cannot
download their e-mails.  Inside the office there is no problem.  At first I
thought that it was a temporary problem either with internet or a dodgy
Microsoft update - maybe it is nothing to do with SME server!

BUT - one user in Belgium, one in France, one in UK, each on a different ISP.

They have each a Laptop - XP Home,e-mail using Outlook Express, connecting via
a VPN connection to send/receive their e-mail.  I know that there is sometimes
a problem with Outlook Express and large mail attachments, but this is not the
case.  What is happening, is that they connect, begin downloading their mail,
and then the connection "freezes" - nothing more is sent or received, sometimes
as little as a few kb received, sometimes a few hundred.

Server is Dell Poweredge, about 1 year old.

Maybe there is no problem with SME.

I have tried to look at the log files, but I don't really know what I am
looking at.  If you need me to post output of log files, please say how and I
will do it.

Thanks in advance.

[mercyh]

All other VPN connections work fine? (can browse network shares and login to shares on the SME)

Are you using SME's VPN or a router/gateway VPN?

Are you using IMAP, IMAPS, POP3 or POPS to download mail? (if you are using secure it might be a certificate that renewed and has not been installed)

Would you be so kind as to attach the bugtracker link?

[dave simmons]

Hi,

Thank you for your very fast reply.  I'll try to answer as best I can.

Regarding VPN, we only use it for mail.  I can try it tomorrow to map a network drive over VPN and try to copy a file.

Using SME VPN.  No router/gateway - SME on fixed public IP.  (There is a router - Cisco - but this is managed by our ISP).  Then a switch (we have 8 public IP addresses).  Then the SME.

We're using standard POP3 to download mail. I don't think we have any certificate installed (but I don't know!).  If it's normally installed by SME then we have one (but then why should it change/disappear?).  It should be a standard SME 7.3 server without any added contribs, all updates applied.

I don't know how to link, the bug number is 4161 - but the full text I have included in my previous post.

Thank you again for your help.

[mercyh]

What is happening, is that they connect, begin downloading their mail,
and then the connection "freezes" - nothing more is sent or received, sometimes
as little as a few kb received, sometimes a few hundred.

This seems to me to indicate that the vpn is working and the e-mail client is seeing the server. Otherwise you would get a server_not_found error from Outlook Express.

Have the users tried to login with webmail using the VPN address that outlook express is using?

for example: if outlook express uses LAN address 192.168.X.X as it's server name can the user go to:

http://192.168.X.X/webmail

login with their username and password and get their mail?

[brianr]

Here is a link to the bugtracker entry:

http://bugs.contribs.org/show_bug.cgi?id=4161

This sounds as if it could be the VPN freezing problem that various people has experienced over the years (including myself for a period).

This may be relevant (and is current)

http://bugs.contribs.org/show_bug.cgi?id=3984

The bugtracker is the correct place to pursue this.

[dave simmons]

BrianR - I agree with your comment about the bug tracker but I'm a bit disappointed that my post on the bug tracker 7 DAYS AGO didn't generate any response, while a post here gets 2 responses inside a half hour.  Makes me wonder a bit about the relevance of the "don't report problems here" in red letters above.

We've never had any problem with VPN before.

MercyH - I will have to try this tomorrow - I'll post results.  If it helps, webmail on the public IP still works perfectly (no VPN involved of course).

Thank you both for your very fast responses.  I'm a very happy user of SME.

ADDED:  E-mail DOES work - eventually.  They can get their mail, but it takes several attempts before it succeeds.

[mercyh]

Dave,

I don't want to steer you away from the bugtracker as all SME problems must end up there to be fixed. I find that many of the forum questions are not SME problems at all but basic networking.

I would suggest one more thing to test to help determine if your problem is VPN or not.

When your user does the Webmail test indicated below have them run

ping 192.168.x.x -t

from the command prompt on the windows machine that is connecting to the server.

(Ctrl-C will cancel this continuous ping)

If the webmail test works, run the ping while attempting to download mail in outlook express. If e-mail traffic stops the ping, you will need to wait for a fix from the bugtracker. It would also be helpful if you would add your experience to the active VPN bug if this turns out to be the problem.

If it helps, webmail on the public IP still works perfectly

I would expect this if the problem is vpn or POP3 server related.

1. If webmail works across the VPN I would suspect POP3 authentication, Client etc.

2. If webmail does not work across the VPN or PING loses connection, I would suspect VPN connection, or network connection problem.

edit

ADDED:  E-mail DOES work - eventually.  They can get their mail, but it takes several attempts before it succeeds.

This was added while I was typing my post. I think you need to weigh in on the active bug as it sounds like you VPN is sporadic. End edit

[dave simmons]

MercyH,

Thank you for your reply.  Unfortunately we cannot test this tonight as my 3 guys are all here today and tomorrow.  I will go to a friend tomorrow with one of the laptops and test it from there.

I also had doubts about whether the problem was from SME or not.  It seems to be an intermittent problem - sometimes they can download mails the first time, sometimes they have to try many times.  These are not normally big mails - no big attachments.

I will post the results tomorrow.

Thanks again.

ADDED:  Have looked at the VPN bug post, and if I understand it correctly, this is about making an outgoing VPN connection from behind a SME server.  What we are doing is connecting to a SME server from outside, using the SME VPN capability.  Or maybe I didn't understand the bug?

[brianr]

ADDED:  Have looked at the VPN bug post, and if I understand it correctly, this is about making an outgoing VPN connection from behind a SME server.  What we are doing is connecting to a SME server from outside, using the SME VPN capability.  Or maybe I didn't understand the bug?

Yes you are correct, however my experience is that these sort of VPN issues have come up in the past, and I think are related to the server loosing VPN packets occasionally, or in one case previously, timing out before a slow connection had time to respond.   However the devs could help you much more (but only through the bugtracker). Perhaps this little flurry will attract one.

[mercyh]

You are correct, that bug is possibly not relevant. We will see what tomorrow tells us.

[dave simmons]

Good news - I've now tried twice - yesterday and today - and there were no problems.  Pinging, VPN, file transfer - all works fine.  Maybe was a problem with our outgoing internet connection (mail within the office was no problem).

I don't think it was a SME problem.

BrianR and Mercyh - thanks for your replies and advice.