Weblog entry #22 for eric
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For the moment, I'm testing on a test domain but before I switch all my real domains, I have a problem: what if my server crashes and i'm not online (sometimes i'm on vacations away from internet)?!!
I need a backup mx...
But for the moment my searches returns nothing about backup mx, free (or affordable). Do you know any service?
I know running a backup mx is not a simple task, and it's better not have one than a bad one, but... I think I can allways filter all the mails coming from the backup mx on my managed one, and my main problem is disponibility.
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You don't need a backup MX you need a reliable mail server, on a reliable connection.
If you can't set one up I suggest you use one of the many free email servers out there. Googlemail's reliability is pretty good, as is AOL's.
Backup MXes are complex beasts to configure these days, and mandate that your spam filtering (for the spam accepted on the backup MX) is accept everything then put it in the spam folder or delete it. Which is far worse than refusing suspected spam, as false positives will never be seen in the spam folder.
Probably easier to use one of the high availability solutions to ensure that the mail server is fully redundant.
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I would second this advice, and also remind you that SMTP is a lovely service from a reliability point of view.
If your mailserver goes down for an hour or two? No big deal as well-behaved SMTP servers will queue messages destined for you until it comes back.
(OK some SMTP servers don't do this properly, but its a nice thing to remember if you do ever have an outage for a few minutes/hours. You don't get that freedom with DNS, Web and other services.)
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I understand what you say.
The fact is running my own mail server, learning about it (install, conf and management) is something that interests me and wanted to do for several years... postponing and postponing until now.
And that I don't want anymore to rely on big email providers (google, yahoo or... AOL (i don't ever imagine AOL as a still existant company in fact :)).
My main 'problem' is the fact that I only own one virtual server and I use it for several tasks: public websites, code repositories but also private tasks like handling bookmarks or collecting feeds, irc connection.
Like Steve said, I don't think my mail servers/processes are the problem, they are reliable but other processes on my server can crash/freeze and put my poor little virtual server down... that's my principal preocupation.
If I understand what you say I should first securize my mail servers before thinking about a backup mx... well, you must be right :) Maybe it's time for a second little virtual server just to run my mail server: I hope running only e-mail tasks will limit crash risks.
This has some financial costs though but... independance has a price...
Another idea is running without backup MX mainly, and when I am far from internet a long time run one for example at home (with synchronised configuration (domains, users, rules)).
Thanks for your comments, I'll start looking at VPS prices to see if this solution is possible.
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The only way to run a proper backup MX these ways is to set up another machine that has identical spam filters and knows which users are valid. You then need to accept all mail from that backup MX, no exceptions.
Running a "dumb" backup MX will result in spammers being able to bypass your spam filters (if they run at SMTP time) and backscatter from spam to invalid addresses. It is certainly better for the Internet as a whole to not do that.
If your machine is really going to be down for 5 hours, I think some bounces are a rather small problem, especially when the other option is that the mail sits in a queue on a backup MX, you are unable to read it since your primary is down and the sender has no idea his mail has not reached you.
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Those are sometimes quite irritating for anyone who is trying to learn something new..
Anyway, I don't think there are many specific "ready for action" mx backup server software packages out there, but the good news is, that you only need to setup a plain standard smtp server, and configure it to forward all mail to your main mx. Most good smtp servers can be configured to wait a long time, before giving up retrying the forwarding of mails, so a couple of hours/days/weeks of downtime should not be a problem, unless it is a mail you are waiting for (but then you should have the means to reboot your primary server).
When that is said, I must agree with some of the posters, that setting up a "dumb" mx backup is stupid. The spammers know what mx to choose, so don't expect them to be "nice" and always try the first one.
But no one ever suggested that you replicate the spam checking to your backup server. It should be easy, because after all, you are running both servers and logic dictates that the backup server will be pretty much like the main server, both in software and configuration.
So go ahead, set up a "clone" mail server, and configure it to be a forwarder, then all should be good.
And remember to set up replication of spamfilters, user accounts, blocklists, etc. from the main server to the backup.
Last, I must say that many of the commercial mx backup service providers are cheaper than renting an extra vps, but then you get THEIR spam filter, what if you want better control?
Who is to say that any commercial mx-backup service is the best in spam filtering?
Sometimes you want full control - and it feels great to be able to change a config file and immediately see the result, rather than waiting hours for a filter to reload on some lame server out there ;)
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