Home page > Debian > On mail servers and google spam filter..

On mail servers and google spam filter..

Saturday 3 April 2010, by Toots

The worst April’s fool ever, on which I will not comment here, has forced me to quickly move the services on my previous machine.

Among them was the email services, which I fear the most.

Configuring again a postfix server, I realize again how arcane its configuration is. Email is probably, with nttp and unix, one of the oldest paradigm in modern computing, and you feel it.

I understand that email used to be intrinsicly linked with unix account. But, come on, those were the days where you would login to a mainframe, way before personal computers.

So, why do you need to know about all sort of server-wide files, like /etc/aliasee and /etc/mailname ? Why do you need to have to tweak the server-wide accounts and login system to create new mailboxes ?

In 99% of the situations now, email accounts do not corresponds to anything on the server, so why keeping all sort of arcane stuff that make the configuration of a mail server so delicate ?

On a side note, I would like to share 3 questions.

First is this idea of using gmail as a spam filter service. You register your address, say joe@doe.com with your joe.doe@gmail.com and you tell your mail server to redirect all the mail to joe@doe.com to joe.doe@gmail.com.

Then in gmail’s interface, you ask gmail to redirect all mails to joe@mail.doe.com. Eventually, the mail at mail.joe.com is delivered to the local inbox.

This allows to use gmail as a spam filter loop. However, I have no idea if this is something already known and if gmail administrators will like it. Lazy web, what do you think ?

Second is the following parameters for postfix: reject_non_fqdn_recipient and reject_unknown_reverse_client_hostname. I wonder if I may loose some mail using them.. Any idea ?

Third is that I wanted to configure the old server to relay anything on the new, and filter there. But, as much fuzz there is about open relay, I was not able to configure my postfix as an open relay.. Any idea on how to do it ?

8 Forum messages

  • On mail servers and google spam filter.. Le 3 April 2010 à 17:18 , by Dmitrijs Ledkovs

    Easiest thing ever =)

    Set up gmail address, add your @example.com domain name to it. On @example.com don’t set up a mail server at all just something that redirects to @gmail.com without spoiling headers to much. (or sign up for Google Apps for domain).

    Then in Gmail or Thunderbird you can send emails from: @example.com and read your mail of gmails imap or pop3. This way you will use gmail’s smtp.

    You can also set up smtp on your server and make Gmail use that when sending emails from @exmaple.com if you don’t want to leak that you are using gmail when using web-interface as well.

    So in general make @example.com an alias to @gmail.com & use gmails imap,pop3,smtp (and optionally your smtp)

    Reply to this message

  • On mail servers and google spam filter.. Le 3 April 2010 à 17:48 , by Luke Faraone

    I don’t personally see a problem with it; I do it already for mailing list filtering for a few projects I work with. It isn’t explicitly denied in their ToS, and as long as you aren’t dealing with a (very) high amount of mail, you should be fine.

    Reply to this message

  • On mail servers and google spam filter.. Le 3 April 2010 à 17:49 , by Marius Gedminas

    Mail is hard, yes.

    I don’t use gmail as a spam filter myself, but one of my coworkers did. (Later she switched to reading her email directly in gmail.)

    I wonder if reject_non_fqdn_recipient might drop emails from local system services such as cron. I’m not sure what exactly reject_unknown_reverse_client_hostname does, but I’d be worried it might lose legitimate mail. I don’t have any hard data or real arguments, just a gut feeling.

    Greylisting might be a better way to reduce the amount of spam you get.

    Relaying your mail form an old server to a new one is just fine; that’s precisely how backup MXes work. On the old server remove the email domain from mydestination and add it to relay_domains. You may also want to configure your DNS to give the old server as a secondary MX. Also you’ll want to make sure both your mail servers have the same kind of spam filtering; things like greylisting are a bit pointless if only one of your MXes does that.

    Reply to this message

  • On mail servers and google spam filter.. Le 4 April 2010 à 01:17 , by Russell Coker

    reject_unknown_reverse_client_hostname is not a good idea.

    Lots of ISPs are offering services that don’t support reverse DNS. Of the ones that do support it some take ages to process requests. This means that there are plenty of well configured mail servers which are not spam sources that don’t have reverse DNS working correctly (if at all).

    I used to block on such things but gave up some time ago, there were too many false-positives.

    More recently the reverse DNS for my mail server was broken and I’m not sure that I can fix it without more money being paid.

    Reply to this message

  • On mail servers and google spam filter.. Le 6 April 2010 à 10:55 , by managementboy

    I have been using gmail as my "spamkiller" and backup for a few years now. Even when my home server is offline I am able to use gmail to keep working, which is nice.

    Reply to this message

  • On mail servers and google spam filter.. Le 8 April 2010 à 02:43 , by budiwijaya

    You can try assp.sourceforge.com though.

    Reply to this message

Reply to this article