On Wed, Mar 20, 2002 at 08:52:25PM +1100, Peter Rundle wrote: > >What do other people with perm connection who run their own mail > >server do for secondary/backup? (ie. secondary mx) > > My suggestion is that you *DON'T*! > > Why not you ask? Think about how the mail system works. Someone sends > a mail to you, it goes from their desktop/mail client of choice onto > the mail queue of their outbound smtp server. The server then does an > MX lookup of the domain and get's your mail servers IP. If it can't > establish a connection to your machine it will then queue the mail and > retry every hour for up to four days. (this is dependant on the mail > system config obviously but that's the recommended standard). If your > mail system is still not up then the sender gets a bounce saying you > didn't get their mail.
Not always. Lots of (small) companies/business run dialup mail servers, which are configured to do their own forwarding (ie, not using a smarthost at their ISP). These mail servers may connect to the internet every X hours (say, 4, 6 or 12 hours) and attempt to send the mail. If they can't, they will re-spool it as you say, and then try again in another X hours. Of course, if X is something like 6 hours, then it only takes your connection to be down for a few minutes when it tries the first few times, and the message could easily take 24 hours to get to you. Not, the real problem here is that that these people are not using a smarthost (ie, forwarding all their mail into their ISPs mail server), but there's nothing you can do about that... > If however you have a secondary MX then the smtp server, when it can't > contact your box will send it there. And that server does what with the > mail?......Precisely the behaviour of the originating server we just Nope. The difference is that you have some control over the secondary server. You know that it's on a reasonably reliable network, you know that it's permanently connected to the internet (presuming you've picked one that is!), you can find out how often it tries to resend mail, etc. Whats more, when your link does come back up, you can connect to your secondary server, and ask it to instantly send any mail it's got queued for you (with ETRN) - you can't do that without a secondary! The network connection between the secondary and your primary server will also almost always be at least as good, and normally better, than between the host sending the mail and your primary server, which means that when your link comes back up, the mail delivery will frequently be faster from the secondary than from the original sending server. > described. I.E the secondary adds what value? NONE in fact it is worse > than that, consider if the secondary server goes down while your mail is > queued up on it, no mail system at $11/month is gonna have transaction > logging on it so when they recover it, it will be from last nights backup > so all the mail received and queued today for your server will be lost. Yup, thats a valid point. But, given that the secondary will only be used when your server is down (or unreachable for whatever reasons), the chances of this actually being a problem are quite low. Scott. -- SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/ More Info: http://lists.slug.org.au/listinfo/slug
